Submerged floating tunnels with suspension supports (SFTSS) resemble to suspension bridges on lands, which are installed a number of hangers on the main tower and main cables to support the girder. On the other hand, as the SFTSS installed underwater has to resist the buoyancy and the forces in an offshore environment, the main cable was installed at the bottom of the tunnel body and connected with a hanger. The concept of the SFTSS was first proposed by Won et al (2019, 2022). It was found that the SFTSS was generated itself a tuned mass damper (TMD) effect due to the interaction between the body and the main cable. This can induce the vibration of the body to be attenuated according to the offshore environment conditions such as waves and currents, and had a feature that the length between the main towers can be longer than 3 km (Won et al., 2022). The body of the SFTSS was supported by main cables and hangers as aforementioned. In case of the hanger was down by failures, the behavior characteristics of the SFTSS would be changed and be greatly reduced the structure safety. In this study, the behavioral characteristics of the SFTSS were analyzed according to five scenarios on the cable failure.

Recently, medium-sized earthquakes such as the Gyeongju 9.12 earthquake (September 12, 2016, M_L = 5.8) and the Pohang earthquake (November 15, 2017, M_L = 5.4) occurred in Korea, thereby increasing social concern about earthquakes. Because Korea is not located near the Circum-Pacific Belt, also referred to as the “Ring of Fire”, people in Korea are not used to earthquake disasters. Coastal areas in Korea are lined with multiple mega-cities and major industrial facilities. Most of them constructed on landfill, they have a high threat level to the damage to populations and structures leading to complex disasters in the event of an earthquake. However, studies of seismic hazards in ports is incomplete compared with those of onshore sites. Improving the understanding of seismic hazards and characterizing them catching up with related research from various perspectives being actively conducted. In this study, the site-specific response characteristics of the Pohang International Container Terminal in Pohang Yeongil New Port were analyzed using the S-wave energy of 10 sets of ground motions recorded by seismic accelerometers operated by the Ministry of Oceans and Fisheries based on the horizontal-to-vertical spectral ratio (H/V ratio) method. As a result of analysis, the H/V ratio curves show that the peak frequency values for the target site averages 9 Hz, and the natural period values of the site were preliminarily predicted to average 0.11 s. In addition, site amplification characteristics are different based on the seismic wave calculation method. The result can be used as data for identifying ground dynamic characteristics and verifying the site amplification coefficients and design spectrum in the seismic design.

The foundations of offshore wind power can be classified as floating, tripod, jacket, monopile, or gravity-based, depending on the support type. In the case of tripod- and jacket-type supports, the structures require precise construction. There are two main methods for installing substructures: post- and pre-piling. The post-piling method involves moving the completed substructure to the site and fixing it to the seabed by inserting a pile into the leg pile and driving it, allowing it to be constructed without special off-shore equipment; however, the construction period is long. Contrarily, the precision of foundation installation can be improved by installing a pre-piling template, which is special equipment that serves as a basic structure, on the seabed in advance, and subsequently inserting substructures. This study presents a new type of underwater pre-piling template and method for achieving optimal construction environment conditions. Construction precision was analyzed based on the wave condition, current speed, winch speed, wave direction, and current direction while the under-water template was anchored to the seabed. It was found that the wave conditions, winch speed, and vessel type had a significant influence. The results obtained considering the Douglas sea scale show that precise construction could only be achieved within Grade 2 for general barge ships, while jack-up barge ships could be used even at Grade 3 or higher. The higher the winch speed, the more stable construction becomes possible, and jack-up barges show greater constructability than general barges.

The Ministry of Oceans and Fisheries of Korea has installed port seismic monitoring stations, mainly at major domestic trade ports, to enable rapid response to unpredictable earthquakes. Currently, 27 stations operate across 13 ports, including 10 along the West Coast, 10 along the South Coast, and 7 along the East Coast. This study analyzed regional background noise levels using continuous microtremor data collected from 2022 to 2024, based on the Probabilistic Power Spectral Density method. Owing to the soft ground typical of port sites, each seismic station is configured as a paired system consisting of a surface station and a vertically aligned borehole rock station. Results show that surface stations exhibit higher and more variable noise levels within the artificial noise band characteristic of industrial ports compared with borehole stations. Additionally, noise levels remain consistently high across all sites in the mean-period frequency band. The Incheon Port bedrock station demonstrated the lowest and most stable noise characteristics, suggesting its suitability as a reference station for future Horizontal-to-Vertical Spectral Ratio analyses. These findings highlight the importance of quantitative background noise assessment to ensure high-quality seismic data and provide a basis for evaluating site response and long-term noise variability at port facilities.

Lava caves commonly occur in basaltic ground and can compromise roadway stability when present beneath pavements; however, their long-term effects remain insufficiently characterized. This study quantitatively evaluates how lava caves influence pavement behavior using numerical analyses in ABAQUS/CAE. The parameters examined include the presence/absence of a cave, cave width, cover depth, pavement thickness, and load range. Load–settlement curves under a uniformly distributed surface load show that narrower load ranges concentrate stresses and produce larger settlements, whereas wider load ranges disperse stresses and reduce deformation. Classification of deformation behavior using a rutting criterion indicates that plastic soil response dominates under most conditions. A Peak Load Reduction (PLR) index further demonstrates that structural resistance decreases markedly with shallow cover, larger cave width, and narrower load range. Overall, pavement stability above lava caves is governed primarily by cover depth, load range, and cave width, while the effect of pavement thickness is negligible. These findings suggest that, in basaltic terrains, design and maintenance should prioritize subsurface conditions and loading characteristics over pavement thickness.