• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.99-111
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• 2019

To investigate the seismic performance of long-span partially earth-anchored cable-stayed bridge, a super long-span partially earth-anchored cable-stayed bridge scheme with main span of 1400m is taken as example, structural response of the bridge under E1 seismic action is investigated numerically by the multimode seismic response spectrum and time-history analysis, seismic behavior and also the effect of structural geometric nonlinearity on the seismic responses of super long-span partially earth-anchored cable-stayed bridges are revealed. The seismic responses are also compared to those of a fully self-anchored cable-stayed bridge with the same main span. The effects of structural parameters including the earth-anchored girder length, the girder width, the girder depth, the tower height to span ratio, the inclination of earth-anchored cables, the installation of auxiliary piers in the side spans and the connection between tower and girder on the seismic responses of partially ground-anchored cable-stayed bridges are investigated, and their reasonable values are also discussed in combination with static performance and structural stability. The results show that the horizontal seismic excitation produces significant seismic responses of the girder and tower, the seismic responses of the towers are greater than those of the girder, and thus the tower becomes the key structural member of seismic design, and more attentions should be paid to seismic design of these sections including the tower bottom, the tower and girder at the junction of tower and girder, the girder at the auxiliary piers in side spans; structural geometric nonlinearity has significant influence on the seismic responses of the bridge, and thus the nonlinear time history analysis is proposed to predict the seismic responses of super long-span partially earth-anchored cable-stayed bridges; as compared to the fully self-anchored cable-stayed bridge with the same main span, several stay cables in the side spans are changed to be earth-anchored, structural stiffness and natural frequency are both increased, the seismic responses of the towers and the longitudinal displacement of the girder are significantly reduced, structural seismic performance is improved, and therefore the partially earth-anchored cable-stayed bridge provides an ideal structural solution for super long-span cable-stayed bridges with kilometer-scale main span; under the case that the ratio of earth-anchored girder length to span is about 0.3, the wider and higher girder is employed, the tower height-to-span ratio is about 0.2, the larger inclination is set for the earth-anchored cables, 1 to 2 auxiliary piers are installed in each of the side spans and the fully floating system is employed, better overall structural performance is achieved for long-span partially earth-anchored cable-stayed bridges.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.589-597
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• 2023

Floating debris in large quantities from land during heavy rainfall has adverse social, economic, and environmental impacts, but the monitoring system for the concentration area and amount is insufficient. In this study, we proposed an efficient monitoring method for floating debris entering the river during heavy rainfall in Daecheong Lake, the largest water supply source in the central region, and applied remote sensing techniques to estimate the standing-stock of floating debris. To investigate the status of floating debris in the upper of Daecheong Lake, we used a tracking buoy equipped with a low-orbit satellite communication terminal to identify the movement route and behavior characteristics, and used a drone to estimate the potential concentration area and standing-stock of floating debris. The location tracking buoys moved rapidly during the period when the cumulative rainfall for 3 days increased by more than 200 to 300 mm. In the case of Hotan Bridge, which showed the longest distance, it moved about 72.8 km for one day, and the maximum moving speed at this time was 5.71 km/h. As a result of calculating the standing-stock of floating debris using a drone after heavy rainfall, it was found to be 658.8 to 9,165.4 tons, with the largest amount occurring in the Seokhori area. In this study, we were able to identify the main concentrations of floating debris by using location-tracking buoys and drones. It is believed that remote sensing-based monitoring methods, which are more mobile and quicker than traditional monitoring methods, can contribute to reducing the cost of collecting and processing large amounts of floating debris that flows in during heavy rain periods in the future.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.104-108
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• 2009

As the demands of ocean resource development increase, many offshore structures are required. To cope with the active ocean developments, many types of construction methods have been applied for offshore facilities, including oil, gas and harbors. One of the challenges is to transport and install the heave bridge caisson. Several construction methods are well understood. However, for the sake of safety and reliability, the F/D installation method can be utilized. While the caisson is carried by an F/D, the mooring force of the tug boat and the structure stability from exiting motions in the dock should be checked against external loadings and sea conditions. The external loads can be classified with wind force, current force, and wave force. In the stability analysis, transportation velocity and draft of F/D are important factors. The dynamic stability and hook load for crane barge installation for the same caisson are also studied. Considering external loads and dominant factors, the stability of caisson during transportation has been investigated.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.421-426
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• 2007

Recently, the defect maintenance period of the new construction structure was extended from 5 years to 10 years. And according to change of realization on the quality of construction and maintenance, a development of semi-permanent method of construction is required for maintenance of blind parts of underwater structure, such as bridge, dam, harbor, etc. In this study, we proposed a floating type sector dry caisson, which is effective to the maintenance of submerged large structures. These large structures were being maintained incompletely, partly due to unskilled divers and difficult working condition. Considering the easiness of access to the maintenance area and the cost for set up the working structure, especially for the case of structure slabs close to the sea surface and harrow pile span structures, we developed and introduced a sector dry caisson instead of the full caisson structure. By doing this, it is easy to move out the caisson rapidly in emergence case. Therefore, we expect that the floating sector caisson will contribute to reduce working time and improve the quality of underwater work in future days.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1273-1287
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• 2014

Plates are most widely used in the hulls of floating concrete structures, bridge decks, walls of off-shore structures and liquid storage tanks. A method of analysis is presented for the determination of load-deflection response and ultimate strength of high-strength steel fiber reinforced concrete (HSSFRC) plates simply supported on all four edges and subjected to combined action of external compressive in-plane and transverse loads. The behavior of HSSFRC plate specimens subjected to combined uniaxial in-plane and transverse loads was investigated. The proposed analytical method is compared to the physical test results, and shows good agreement. To predict the constitutive behavior of HSSFRC in compression, a non-dimensional characteristic equation was proposed and found to give reasonable accuracy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.17-18
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• 2014

Wave energy generation system is sorted as oscillating water chamber type, over topping device type and wave activating body type. The wave activating body type converts from wave energy to kinetic of the machine one and the power generation amount increases while the motion of a activating body increases. In this paper the wave energy convertor consists of a main body which has a generation system and the activating body. They are connected by a bar type bridge. The twisting moment and angular velocity at a shaft of convertor are calculated when various condition of the incident wave, a diversity of connection methods between the main body and the activating body. It can be used as basic idea for determining the design of wave activating body type convertor.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.105-114
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction of 9 new ports and renovation of the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built of steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions of structures and increased underwater construction period. for the purpose of cutting down the government budget, it is necessary to extend the life cycle of the existing structures. We developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction of maintenance expenses and time for anti-corrosion work but also better protection. This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.

• Journal of Urban Science
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• v.11 no.2
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• pp.19-24
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• 2022

Conventional RC beams for crossing small and medium-sized rivers do not have a cross-sectional area, so the floating debris is accumulated and disasters such as damage to bridges occur. To improve this, the PSC method was invented. However, this also had problems such as transverse curvature, increase in dead weight due to cross-sectional shape, and negative moment generated during serialization, so it was necessary to develop a new type of girder. Therefore, it was intended to propose a LIT(Leton Interaction Thrust) girder bridge that is safer and has better performance than the conventional PSC girder with improved section efficiency. Unlike existing girder bridges, the LIT girder has the feature that the change in the strands of the entire girder occurs only in the vertical direction when the first tension is applied because the tendon arrangement is symmetrical by applying the raised portion. In addition, slab continuation generates a secondary moment that is advantageous to the continuous point, effectively controlling the negative moment and preventing the corrosion of the tendon. The dimensions of the cross section were determined, and the arrangement of the strands was designed to conduct structural analysis and detailed analysis. As a result of the structural analysis, the stress of the girder showed results within the allowable compressive stress, and the deflection showed the result within the allowable deflection. showed results. In addition, a detailed analysis was performed to examine the stress distribution around the girder body and the anchorage area and the stress distribution of the embossed portion, and as a result, the stress of the girder body due to the tension force showed a stable level.

• Structural Engineering and Mechanics
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• v.31 no.4
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• pp.371-382
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• 2009

The concrete plates are most widely used structural elements in the hulls of floating concrete structures such as concrete barges and pontoons, bridge decks, basement floors and liquid storage tanks. The study on the behavior of high-strength fiber reinforced concrete (HSFRC) plates was carried out to evaluate the performance of plates under in-plane and transverse loads. The plates were tested in simply supported along all the four edges and subjected to in-plane and traverse loads. In this experimental program, twenty four 150 mm diameter cylinders and twelve plate elements of size $600{\times}600{\times}30$ mm were prepared and tested. Water-to-cementitious materials ratios of 0.3 and 0.4 with 10% and 15% silica fume replacements were used in the concrete mixes. The fiber volume fractions, $V_f$ = 0%, 1% and 1.5% with an aspect ratio of 80 were used in this study. The HSFRC mixes had the concrete compressive strengths in the range of 52.5 to 70 MPa, flexural strengths ranging from 6.21 to 11.08 MPa and static modulus of elasticity ranging from 29.68 to 36.79 GPa. In this study, the behavior of HSFRC plate elements subjected to combined uniaxial in-plane and transverse loads was investigated.

• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.447-455
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction cf 9 new ports and renovation cf the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built cf steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions cf structures and increased underwater construction period. For the purpose cf cutting down the expense cf government budget, it is necessary to extend the life cycle of the existing structures. Therefore, we developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction of maintenance expenses and time for anti-corrosion work but also better protection This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.