Maintenance systems for port and fishing port infrastructures are rapidly shifting toward digital transformation and digital twinbased asset management. In this context, terrestrial LiDAR (TLS) has emerged as a key technology for acquiring high-precision three-dimensional digital assets. However, TLS data acquisition in coastal environments is challenging due to tidal variations and the coexistence of fixed and floating structures. This study proposes a practical workflow for high-precision 3D digital modeling and point-cloud data optimization of port facilities using TLS. Field experiments were conducted at Gungpyeong Port using a Leica RTC360 scanner across a 300 m section with 32 scanning stations. To improve reliability under dynamic marine conditions, a threestage registration strategy—field alignment, office precision registration, and dynamic-object segmentation followed by re-registration—was applied. The registration error was reduced from 45.2 mm to 4.3 mm RMSE after the final refinement. In addition, tidal observations confirmed vertical displacement of floating structures of up to 895 mm during the scanning period. For practical use in CAD/BIM environments, a 10 mm uniform sampling technique was applied, reducing the data volume from 6.6 GB to 1.1 GB (83% reduction) while maintaining geometric accuracy within 9.8 mm. The proposed workflow provides a reliable foundation for digital-twin-based monitoring, safety inspection, and intelligent maintenance of port infrastructures.

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.

This study investigates the dynamic behavior of a suspension-type submerged floating tunnel (SFT) under irregular waves using OrcaFlex simulation. Key design parameters(main cable arch height, arrangement angle, submergence depth, and unit weight) were analyzed.The results demonstrate that an arch height of 80 m is optimal for stability, whereas an excessive height (150 m) significantly increases displacement and internal forces. Increasing the arrangement angle to 30° effectively mitigates sway motion, and deep submergence (100 m) drastically reduces wave-induced acceleration. While heavier cables suppress vibration, they induce higher static loads, indicating a trade-off relationship. Consequently, this study proposes an optimized configuration (80 m arch height, 30° angle, and deep submergence) to ensure structural safety and serviceability in deep-sea environments.

The Ministry of Oceans and Fisheries (MOF) in Korea established the Port Alert System for Seismic Response (PASS) in 2018 to enhance the nation's capacity to respond to earthquakes and tsunamis affecting major trade ports. PASS serves as a core platform for intelligent situational management during seismic events by enabling the rapid dissemination of critical information for situational assessment and decision-making. Through this system, quick and effective responses to earthquake emergencies in port environments are made possible. This paper provides an overview of the smart disaster management system for Korean ports and presents the main developments in response-stage management based on PASS.

As of May 2023, the Ministry of Oceans and Fisheries (MOF) in Korea is operating a port alert system for seismic response at 28 stations centered on 13 trade ports to monitor the stability of the port structures rapidly after earthquakes. The peak ground acceleration according to measuring stations can be analyzed using the data processing algorithm. Based on this, we review the excess rate of the design acceleration for port structures during earthquakes and utilize them as an emergency safety check. It plays a significant role in operating intelligent situation management under earthquake disasters. This system makes it possible to make quick decisions and respond to earthquake disaster fields in ports. This paper overviews the smart disaster management system for ports in Korea, with priority given to the response stage. And it introduced the application of these measurement data processing algorithms.

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.

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.

This paper presents an investigation of the structural stability of cable-stayed bridges based on nonlinear analysis. In general, girders and masts of cable-stayed bridges are always subjected to compressive forces due to pre-tensioned stay cables. Cable-stayed bridges exhibit various geometric nonlinearities, such as the cable-sag effect, beam-column effect of girders and masts, and large displacement effect. In this study, the characteristics of the structural stability of cable-stayed bridges are investigated. Because of various geometric nonlinearities, nonlinear finite element analysis should be performed for stability analysis instead of conventional eigenvalue analysis. Furthermore, the initial shape analysis should be performed prior to live load analysis in order to consider the dead load condition rationally. A two-step analysis method, developed based on the theory of nonlinear finite element method, is presented in this study for stability analysis under live load cases. An intensive series of parametric studies is subsequently performed using three-span cable-stayed bridges. The main buckling modes are classified depending on the location of the critical members. Also, the effects of cable arrangement, girder-mast stiffness ratio, area, and the number of cables on the structural stability are extensively investigated.

An appropriate mooring system and tunnel body are required to ensure the dynamic stability and serviceability of submerged floating tunnels (SFTs) under various environmental loads. This paper presents a feasibility study of SFTs with vertical and inclined combined tethers. The basic concept of this system is to provide the vertical and horizontal stiffness of the tunnel using the vertical and inclined combined tethers. To evaluate this type of SFT, a hydrodynamic analysis was performed in the time domain using the finite element program ABAQUS-AQUA. The spacing of the tethers and inclination angle of the inclined tethers were considered as the parame-ters. An irregular wave with a 100-year return period was considered as the environmental load. Through the numerical analysis, the time series for the tether stress, tunnel displacement, and internal forces were obtained. Based on the obtained structural response, the adequacy of the strength and fatigue design of the vertical and inclined tethers combined mooring system was investigated. Through an analytical study, it was found that this mooring type could be effectively applied, owing to its structural efficiency. According to the numerical analysis, the combined mooring system satisfies the design conditions when the tether spacing is less than 40.0 m and inclination angle is 45.0 degrees.

Recently, medium-sized earthquakes such as the Gyeongju 9.12 earthquake (September 12, 2016, ML = 5.8) and the Pohang earthquake (November 15, 2017, ML = 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 tension leg method is typically used for the mooring of submerged floating tunnels (SFTs). These tunnels may have mooring lines and foundations installed very close together, depending on the wave conditions. Sometimes, the construction cost can be increased by the foundation design. To overcome these weaknesses, a suspension SFT using the mechanism of a suspension bridge has been proposed. In this approach, the tunnel body is connected to fixed towers at both ends. Two main cables are installed for controlling the tunnel motion. The main cables are connected to the tunnel using hangers. The main cable is a steel pipe and filled with water to increase its weight. The main cables are arranged in an arch shape for controlling the buoyancy weight ratio (BWR) of the tunnel body. The present study analyzed the vibration characteristics of a suspension SFT using the free vibration analysis and time-domain analysis techniques. The study demonstrates that the SFT has excellent self-vibration control. The suspension SFT affected tuned mass damping via the interaction between the tunnel body and main cables.

A submerged floating tunnel, consisting of a tunnel and tethers, is effective as a sea-crossing transportation infrastructure element in deep-water environments. Instead of fixed columns, the tunnel is positioned by the tethers. This means that a significant structural performance degradation in the mooring can directly induce a change in the structural state; moreover, the failure of the tethers will eventually lead to structural instability. Therefore, structural health monitoring is essential for the tethers, as well as for the main tunnel segments. Unfortunately, there are limitations to the applicable sensors for measuring the structural responses required to evaluate the structural state and for estimating the structural damage to the tethers, owing to the environmental characteristics. Therefore, it is necessary to develop and apply an effective damage detection method to secure structural safety. Accordingly, in this study, an advanced damage detection method is proposed for the tethers of submerged floating tunnels based on the convolutional neural network (CNN). The damage detection estimation model is based on a convolutional neural network framework consisting of input, output, and hidden layers for training, validation, testing, and application. The model is trained using structural response data obtained by a hydrodynamics-based time-domain analysis considering various waves and tether damage cases. For successful training, the time-domain structural response data are converted to discretized image data. The accuracy of the proposed CNN-based damage detection models for the various damage rates and noise levels was evaluated. The accuracy of the CNN–S-16-Model which uses 16 sensors with 0–5% level noise signals ranges from 98.4 to 100.0% for 50% damage, from 97.6 to 100.0% for 30% damage, and from 92.0 to 100.0% for 15% damage to the tethers. The noise level significantly affected the damage detection accuracy for the relatively low damage rate cases. Therefore, rational noise filtering is required to enhance the accuracy for minor damage cases.

This paper presents an inelastic buckling behavior analysis of rectangular hollow steel tubes with geometrical imperfections under elevated temperatures. The main variables are the temperature loads, slenderness ratios, and exposure conditions at high temperatures. The material and structural properties of steels at different temperatures are based on Eurocode (EN 1993-1-2, 2005). In the elastic buckling analysis, the buckling strength decreases linearly with the exposure conditions, whereas the inelastic buckling analysis shows that the buckling strength decreases in clusters based on the exposure conditions of strong and weak axes. The buckling shape of the rectangular steel column in the elastic buckling mode, which depicts geometrical imperfection, shows a shift in the position at which bending buckling occurs when the lower section of the member is exposed to high temperatures. Furthermore, lateral torsional buckling occurs owing to cross-section deformation when the strong axial plane of the model is exposed to high temperatures. The elastic buckling analysis indicates a conservative value when the model is exposed to a relatively low temperature, whereas the inelastic buckling analysis indicates a conservative value at a certain temperature or higher. The comparative results between the inelastic buckling analysis and Eurocode 3 show that a range exists in which the buckling strength in the design equation result is overestimated at elevated temperatures, and the shapes of the buckling curves are different.

A double-skinned composite tubular (DSCT) column, which is an internally confined concrete-filled tubular column with a hollow section, has been developed for efficient use of materials that reduce self-weight and enhance seismic performance. It exhibits excellent material behavior with ductility owing to the confinement induced by outer and inner steel tubes. This study conducted axial compression tests considering the effects of steel tube thickness and hollow diameter ratios of DSCT columns on the material behavior of confined concrete under pure axial compression on concrete cores. From the axial compression tests, various combinations of outer and inner tube thicknesses and two different hollow section ratios were considered. Additionally, confined concrete material behavior, axial strength, failure modes, and ductility of DSCT columns were evaluated. Based on this study, it was concluded that the tests show a good correlation with peak strength and shapes of nonlinear stress-strain curves presented in literature; however, the thinner outer and inner steel tubes may reduce the ductility of DSCT columns when using thinner outer and inner tubes and higher confined stress levels. Finally, the minimum thickness requirements of the steel tubes for DSCT columns were discussed in terms of strength and ductility of test specimens.

A type of submerged floating tunnel (SFT) with a dual section was proposed in this study, and its hydrodynamic behavior was investigated using an analytical method. Unlike existing SFTs with a single section, a dual-SFT with two tunnel bodies requires the analysis of various aspects. To this end, the use of a finite element analysis technique was verified by comparison with previously reported hydraulic test results. Based on this, a free vibration analysis and parameter study were conducted for the dual-SFT under irregular waves. The behavior characteristics of the SFT were analyzed by selecting representative variables, such as the buoyancy-weight ratio (BWR), current speed, spacing of the tunnel body, and wave steepness. The results confirmed that the BWR, wave steepness, tunnel spacing, and current flow values for which slack occurred changed according to the tether-mooring method. In addition, the resistance characteristics under waves and currents were very dissimilar according to the two proposed mooring methods.

In recent years, there has been a growing demand for renewable energy that is free of power generation by products to address the global climate and resource limitation crises. Wind power generation is maximizing efficiency through constant research and development, and as the use of large capacity turbines increases, the scale of supporting structure also increases. The structural maintenance of hollow towers, the supporting structure of wind turbines, requires the installation of an opening through which workers can access the tower to check corrosion, cracks, and damage to the tower body. However, these access points can affect the buckling strength of the tower structures due to section loss. In this study, the effects of the opening on the structural stability and ultimate strength of a large diameter cylindrical shell, which could be used as a wind turbine supporting tower structure, were studied through elastic buckling and nonlinear analyses. Based on the analytical results, the effects of the thickness of a collar stiffener around the opening on the structure's ultimate strength were investigated. The results were compared to the design criteria, and through regression analysis, an effective equation to determine the collar stiffener's thickness for large diameter cylindrical shells was proposed based on an opening that satisfied the design strength criteria.

In case of a submerged floating tunnel (SFT), which is difficult to cast in-site underwater con-struction, it is modularized on land and then assembled them in the field. Therefore, it is influ-ential to investigate the structural performance of the joints between the modules. A concept of the steel-concrete composite hollow in the SFT, which stably maintains the joints, has been proposed by applying prestressing method to resist various external loads. In this study, the bending behavior of module joints was experimentally analyzed to evaluate the safety for the bending deformation that is dominant in SFT. Test results show that there is a difference at the module joint portion in the performance depending on whether or not the inner steel tube is connected. The bending stiffness of the module joints in the SFT was very similar but there was a difference in strength. The maximum strength was increased from 700 kN to 1200 kN when the inner tube was connected, and the residual displacement was increased from 15 mm to 40 mm. As a result, in the design of the module joint, depending on the purpose of SFT, it is possible to consider both methods which is allowing the ductility behavior of internal tube and controlling the tight connection. Moreover, the failure criterion of the bending behavior of the module joint can be selected as the maximum load or deformation limit.

To develop an optimum design concept for the submerged floating tunnel (SFT), many studies have evaluated the dynamic behavioral characteristics of submerged structures under various design loads and it has been concluded that rational mooring systems should be applied to very large and long submerged structures for use as transportation facilities. For this purpose, the concept of SFTs moored by laterally inclined tethers anchored to the seabed has been mainly studied. However, the issue of erecting many tethers with individual seabed anchors or piles should be solved for the mooring systems. This study aims to investigate the feasibility of the SFTs moored by inclined tethers attached to fixed towers. The new concept of SFTs, which fundamentally originated from cable-stayed bridges, was proposed for reducing burden of construction of individual seabed piles for each tether. In this study, behavioral characteristics of the SFT under the regular and irregular waves were investigated by performing hydrodynamic analysis in time-domain. For suggesting feasible and acceptable concepts for the transportation facilities, the effects of various geometric design parameters, such as the draft, sectional characteristics of the tunnel, stiffness of the tethers, and inclination of the fixed tower legs on the structural behaviors have been evaluated.

ABSTRACT Lee, B.W.; Won, D.; Kim, D.H., and Park, W.-S., 2021. Model tests for evaluating the bearing pressure of harbor structures using open cell caisson method. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 26–30. Coconut Creek (Florida), ISSN 0749-0208. This study is related to the ground bearing pressure of a caisson-type harbor structure. In particular, it was examined the ground bearing pressure of the harbor structure to which the open cell caisson method was developed to increase stability by interlocking caissons. An experimental study was conducted to confirm the performance for the ground bearing pressure with a construction method that significantly improved the sliding stability of the structure by filling crushed stones between two adjacent open cells. A small scale caisson model and four load cells were used to evaluate the change of the ground bearing pressure due to the action of a horizontal load. The validity of experiment results was confirmed through comparison with numerical results using ABAQUS. As a result of the experiment, it was confirmed that the open cell caisson method showed superior characteristics for the ground bearing pressure compared to the conventional caisson method. As the degree of compaction of crushed stones increased, the ground bearing pressure was further reduced, and an increase in the coefficient of friction on the side wall had a great influence on a decrease. The end bearing pressure was reduced by 46% even in the condition that crushed stones were not compacted and the side wall was not uneven (frictional coefficient 0.47), and in the condition with unevenness (frictional coefficient 0.787), it decreased by 70%. When the condition for compacting fully crushed stones was added, the result was reduced up to 77%.