In this paper, three approachs were developed to find indicator species from the habitat created by coastal structures. These approachs consist of a model of species co-occurrence probability, a model of k-environment...In this paper, three approachs were developed to find indicator species from the habitat created by coastal structures. These approachs consist of a model of species co-occurrence probability, a model of k-environmental factor probability and a composite model. Simultaneously, a case study was conducted in Hsinchu Fishing Port of north-western Taiwan. Based on the aforementioned models, three primary producer species, Ahnfeltiopsis flabelliformis, Chondrus ocellatus and Sarcodia montagneana, were chosen as the indicator species which had the highest co-occurrence probabilities and showed greater tolerance to more critical environment. It is imperative to understand how the three species under particular co-occurring conditions and environmental factors influence the composition of sessile assemblages in coastal water. The results indicate that for the purpose of increasing biodiversity, these models are feasible to find indicator species of artificial structures, and to help make it possible to design coastal structures based on biological considerations. This study provides an innovative approach for further advanced application in the artificial habitat of coast management.展开更多
Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall(M–K)trend test,this study analyzes the linear c...Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall(M–K)trend test,this study analyzes the linear characteristics and nonlinear behavior of the medium-to long-term shoreline evolution of Jinghai Bay,eastern Guangdong Province.In particular,shoreline rotation caused by a shore-normal coastal structure is emphasized.The results show that the overall shoreline evolution over the past 30 years is characterized by erosion on the southwest beach,with an average erosion rate of 3.1 m/a,and significant accretion on the northeast beach,with an average accretion rate of 5.6 m/a.Results of the M–K trend test indicate that significant shoreline changes occurred in early 2006,which can be attributed to shore-normal engineering.Prior to that engineering construction,the shorelines are slightly eroded,where the average erosion rate is 0.7 m/a.However,after shore-normal engineering is performed,the shoreline is characterized by significant erosion(3.2 m/a)on the southwest beach and significant accretion(8.5 m/a)on the northeast beach,thus indicating that the shore-normal engineering at the updrift headland contributes to clockwise shoreline rotation.Further analysis shows that the clockwise shoreline rotation is promoted not only by longshore sediment transport processes from southwest to northeast,but also by cross-shore sediment transport processes.These findings are crucial for beach erosion risk management,coastal disaster zoning,regional sediment budget assessments,and further observations and predictions of beach morphodynamics.展开更多
Sedimentation is one of the most critical environmental issues facing harbors’authorities that results in significant maintenance and dredging costs.Thus,it is essential to plan and manage the harbors in harmony with...Sedimentation is one of the most critical environmental issues facing harbors’authorities that results in significant maintenance and dredging costs.Thus,it is essential to plan and manage the harbors in harmony with both the environmental and economic aspects to support Integrated Coastal Structures Management(ICSM).Harbors’layout and the permeability of protection structures like breakwaters affect the sediment transport within harbors’basins.Using a multi-step relational research framework,this study aims to design a novel prediction model for estimating the sedimentation quantities in harbors through a comparative approach based on artificial intelligence(AI)algorithms.First,one hundred simulations for different harbor layouts and various breakwater characteristics were numerically performed using a coastal modeling system(CMS)for generating the dataset to train and validate the proposed AIbased models.Second,three AI approaches namely:Support Vector Regression(SVR),Gaussian Process Regression(GPR),and Artificial Neural Networks(ANN)were developed to predict sedimentation quantities.Third,a comparison between the developed models was conducted using quality assessment criteria to evaluate their performance and choose the best one.Fourth,a sensitivity analysis was performed to provide insights into the factors affecting sedimentation.Lastly,a decision support tool was developed to predict harbors’sedimentation quantities.Results showed that the ANN model outperforms other models with mean absolute percentage error(MAPE)equals 4%.Furthermore,sensitivity analysis demonstrated that the main breakwater inclination angle,porosity,and harbor basin width affect significantly sediment transport.This research makes a significant contribution to the management of coastal structures by developing an AI data-driven framework that is beneficial for harbors’authorities.Ultimately,the developed decision-support AI tool could be used to predict harbors’sedimentation quantities in an easy,cheap,accurate,and practical manner compared to physical modeling which is time-consuming and costly.展开更多
Beach groynes are structures for erosion protection along sandy coasts near inlets and can reduce the coastal erosion substantially,but open groynes cannot stop erosion completely because sand can be removed from the ...Beach groynes are structures for erosion protection along sandy coasts near inlets and can reduce the coastal erosion substantially,but open groynes cannot stop erosion completely because sand can be removed from the groyne compartments by cross-shore processes.Beach groynes should be designed with sufficient bypassing of sand to minimise erosion.Regular beach maintenance is required to keep a sufficient beach width for recreational purposes.The effectiveness of groyne compartments can be significantly improved by using T-head groynes or by using a submerged sill or breakwater in between the groynes.An economic evaluation shows that the beach maintenance costs over 50 years may be substantially higher than the construction costs of a submerged breakwater.An important parameter to be studied is the longshore transport,which requires detailed information of the wave climate,preferably based on measured data(offshore buoys)in combination with deep water wave modelling.Various models have been used to determine the net longshore sand transport and coastline changes.The design of groynes to reduce coastal erosion is illustrated by three field cases(Atlantic coast near Soulac,France;Lagos coast,Nigeria and Black Sea coast,Romania).These example cases show that beach groynes are effective structures,but sufficient bypassing of longshore sand transport is essential to minimise erosion.Regular beach fills in the groyne compartments may be required at high-energy(exposed)coasts.A submerged or emerged breakwater can be built between the groynes to protect the beach in the groyne compartments against erosion by cross-shore processes.展开更多
A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the tem...A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.展开更多
Flat geotubes are widely used for coastal structures such as seawalls, breakwaters and sightseeing groins, etc.. However, the understanding of the stable mechanism involved in the wave-structure interactions should be...Flat geotubes are widely used for coastal structures such as seawalls, breakwaters and sightseeing groins, etc.. However, the understanding of the stable mechanism involved in the wave-structure interactions should be deepened, and one of the important work is to clarify the stress state of the structure under the wave action. In this article, wave force acting on coastal structures made of flat geotube is experimentally investigated. The required drag, inertia and lift coefficients are especially analyzed from the results of hydraulic model experiments specially designed for geotube structure. Several types of structures made of flat geotubes under wave action have been tested in order to understand the stress state of the geotube fixed to force transducer within different structures. Experimental results show that the wave-induced forces on the instrumented geotube are markedly influenced by wave elements. Meanwhile, the magnitude of horizontal force of adjoining geotube is different at the same time.展开更多
Numerical analysis was made for shoreline evolution in the vicinity ofcoastal structures, including spur dike, detached breakwaters. The nonlinear partial differentialequation was derived, and numerical solutions were...Numerical analysis was made for shoreline evolution in the vicinity ofcoastal structures, including spur dike, detached breakwaters. The nonlinear partial differentialequation was derived, and numerical solutions were obtained by the finite difference method. Thenumerical results show good agreement with previous analytical results.展开更多
The interaction between solid structures and free-surface flows is investigated in this study. A Smoothed Particle Hy- drodynamics （SPH） model is used in the investigation and is verified against analytical solution...The interaction between solid structures and free-surface flows is investigated in this study. A Smoothed Particle Hy- drodynamics （SPH） model is used in the investigation and is verified against analytical solutions and experimental obser- vations. The main aim is to examine the effectiveness of a tsunami-resistant house design by predicting the wave loads on it. To achieve this, the solitary wave generation and ran-up are studied first. The solitary wave is generated by allowing a heavily weighted block to penetrate into a tank of water at one end, and the near-shore seabed is modelled by an inclined section with a constant slope. Then, the SPH model is applied to simulate the three-dimensional flows around different types of houses under the action of a solitary wave. It has been found that the tsunami-resistant house design reduces the impact force by a factor of three.展开更多
This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dim...This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is represented by acoustic type, potential based fluid elements. The elasto-plastic behavior of the soil medium is idealized using Drucker-Prager yield criterion based on associated flow rule assumption. Four nodded plane strain elements are used to model the concrete wall, foundation, subsoil, backfill and seabed zones. Fluid Structure Interface （FSI） elements are considered between the seawater interfaces with the quay-wall and the seabed. Frictional contact elements are employed between the wall and soil interfaces. The numerical model is validated using field measurements available for permanent drifts in a quay-wall damaged during Kobe earthquake. Reasonable agreements are obtained between the model predictions and the field measurements. Non-linear seismic analyses of the selected quay-wall subjected to both near-fault and far-fault ground motions are performed. An incremental dynamic analysis approach （IDA） is used. In general, at least for models examined in the current study, the gravity quay-walls are found to be more vulnerable to near-field, in comparison with the corresponding far-field, earthquakes.展开更多
A fouling study was conducted in coastal waters southwest of the East China Sea between December 2013 and November 2014. A total of 84 species of fouling organisms belonging to 69 genera, 49 families, and 10 phyla wer...A fouling study was conducted in coastal waters southwest of the East China Sea between December 2013 and November 2014. A total of 84 species of fouling organisms belonging to 69 genera, 49 families, and 10 phyla were recorded over the entire year. The community composition was dominated by coastal warm-water species belonging to typical subtropical inner bay communities. The prosperous stage of settlement lasted from April to September, and the adhesion strength of the fouling organisms was the highest in summer. Sessile suspension feeders constituted the main core of settlement for the fouling community. Amphibalanus reticulatus was the most dominant and representative species of fouling organism, and other dominant species included Caprella equilibra, Ectopleura crocea, Anthopleura nigrescens, Stylochus ijimai, Spirobranchus kraussii, Crassostrea angulata, Perna viridis, Jassa falcata, Stenothoe valida, Sphaerozius nitidus, and Biflustra grandicella. The individuals in the fouling community showed a mutual dependence or constraint relationship due to competition for settlement space and food, and they exhibited a particular spatiotemporal distribution in accordance with adaptation to environmental factors. Temperature was the most important environmental factor determining the geographic distribution of fouling organisms. The temperature characteristics of species essentially reflect the differences in the fouling community composition in various climate zones. The species number, settlement stage, and settlement rate of fouling organisms are closely related to water temperature. Local natural environmental conditions（salinity, water currents, light, etc.） as well as human activity（such as aquaculture production） are all important factors affecting the settlement of fouling organisms.展开更多
The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave ...The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave overtopping of Nampo dike by use of Owen model, Van der Meer ＆ Janssen model and Hedges ＆ Reis model for wave overtopping of seawall. Based on the available tidal and wave data for storm surges in 1989, the risk assessment of wave overtopping of the Nampo dike has been carried out by both Level Ⅱ and Level Ⅲ reliability methods. The calculated resuhs show the general agreement of failure probability between the two methods. By utilizing the rehabilitated cross section of Nampo dike, the failure probability of wave overtopping for the Nampo dike after rehabilitation will be rapidly reduced to that of initial design at crest level of 9.0 m with the improved slope from 1 ： 2 to 1 ： 4 at seaside. Since the sea level may only rise 1.0 m in the next few decades, the failure probability of Nampo dike will be still in the safe range.展开更多
The interactions between regular surface waves and a surface-pitching slotted barrier are investigated both analytically and experimentally. A quasi-linear theory is developed using the eigenfunction expansion method....The interactions between regular surface waves and a surface-pitching slotted barrier are investigated both analytically and experimentally. A quasi-linear theory is developed using the eigenfunction expansion method. The energy dissipation within the barriers is modeled by a quadratic friction factor, and an equivalent linear dissipation coefficient, which is depth-varying, wave-height dependent, is introduced to linearize the matching condition at the surface-pitching barrier. By comparing the theoretical results with laboratory experiments, it is shown that the present method can satisfactorily predict the variation of the reflection and transmission coefficients with wave height.展开更多
A linear hybrid model of Mild Slope Equation （MSE） and Boundary Element Method （BEM） is developed to study the wave propagation around floating structures in coastal zones. Both the wave refraction under the influ...A linear hybrid model of Mild Slope Equation （MSE） and Boundary Element Method （BEM） is developed to study the wave propagation around floating structures in coastal zones. Both the wave refraction under the influence of topography and the wave diffraction by floating structures are considered. Hence, the model provides wave properties around the coastal floating structures of arbitrary shape but also the wave forces on and the hydrodynamic characteristics of the structures. Different approaches are compared to demonstrate the validity of the present hybrid model. Several numerical tests are carried out for the cases of pontoons under different circumstances. The results show that the influence of topography on the hydrodynamic characteristics of floating structures in coastal regions is important and must not be ignored in the most wave period range with practical interests.展开更多
The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connecto...The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connectors.Recently,the use of floating piers has increased because of their advantages,such as faster and higher-quality construction,seismic force isolation for a full-scale mooring system,low dependence on local soil conditions and tides,ability to relocate or reconfigure the pier modules during the operation period and 75-100 years of repair-free service.A floating pier consists of a pier,access bridge,mooring system and fender system,each of which comes in many variations to suit different usages and construction considerations.The typical loads used in the design of these piers are dead loads,live loads,mooring loads,fender loads and environmental loads induced by wind,currents and waves.For numerical simulation,three types of piers are used:passenger piers,light-cargo piers and semi-heavy-cargo piers.The selected piers consist of several large pontoons joined by pivots and have a pile-based mooring system.These piers are modeled by SAP2000software as two-dimensional frames that are linked together.As the first step,each type of pier is subjected to loading,and its general behavior is assessed.According to this behavior,the major load combinations are described for the design of piers and analyzed to determine the behavior of the modules.Lastly,according to the analysis results and the safe use and stability considerations,such as the maximum draft and longitudinal gradient,the dimensions of each module in each pier type are presented.展开更多
基金supported by the Science Council under grant number NSC94-2611-E-009-003
文摘In this paper, three approachs were developed to find indicator species from the habitat created by coastal structures. These approachs consist of a model of species co-occurrence probability, a model of k-environmental factor probability and a composite model. Simultaneously, a case study was conducted in Hsinchu Fishing Port of north-western Taiwan. Based on the aforementioned models, three primary producer species, Ahnfeltiopsis flabelliformis, Chondrus ocellatus and Sarcodia montagneana, were chosen as the indicator species which had the highest co-occurrence probabilities and showed greater tolerance to more critical environment. It is imperative to understand how the three species under particular co-occurring conditions and environmental factors influence the composition of sessile assemblages in coastal water. The results indicate that for the purpose of increasing biodiversity, these models are feasible to find indicator species of artificial structures, and to help make it possible to design coastal structures based on biological considerations. This study provides an innovative approach for further advanced application in the artificial habitat of coast management.
基金The National Nature Science Foundation of China under contract No.42071007the Nature Science Foundation of Hainan Province under contract Nos 422RC665,421QN0883,and 423RC553。
文摘Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall(M–K)trend test,this study analyzes the linear characteristics and nonlinear behavior of the medium-to long-term shoreline evolution of Jinghai Bay,eastern Guangdong Province.In particular,shoreline rotation caused by a shore-normal coastal structure is emphasized.The results show that the overall shoreline evolution over the past 30 years is characterized by erosion on the southwest beach,with an average erosion rate of 3.1 m/a,and significant accretion on the northeast beach,with an average accretion rate of 5.6 m/a.Results of the M–K trend test indicate that significant shoreline changes occurred in early 2006,which can be attributed to shore-normal engineering.Prior to that engineering construction,the shorelines are slightly eroded,where the average erosion rate is 0.7 m/a.However,after shore-normal engineering is performed,the shoreline is characterized by significant erosion(3.2 m/a)on the southwest beach and significant accretion(8.5 m/a)on the northeast beach,thus indicating that the shore-normal engineering at the updrift headland contributes to clockwise shoreline rotation.Further analysis shows that the clockwise shoreline rotation is promoted not only by longshore sediment transport processes from southwest to northeast,but also by cross-shore sediment transport processes.These findings are crucial for beach erosion risk management,coastal disaster zoning,regional sediment budget assessments,and further observations and predictions of beach morphodynamics.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(NRF-2021R1A2B5B02002599).
文摘Sedimentation is one of the most critical environmental issues facing harbors’authorities that results in significant maintenance and dredging costs.Thus,it is essential to plan and manage the harbors in harmony with both the environmental and economic aspects to support Integrated Coastal Structures Management(ICSM).Harbors’layout and the permeability of protection structures like breakwaters affect the sediment transport within harbors’basins.Using a multi-step relational research framework,this study aims to design a novel prediction model for estimating the sedimentation quantities in harbors through a comparative approach based on artificial intelligence(AI)algorithms.First,one hundred simulations for different harbor layouts and various breakwater characteristics were numerically performed using a coastal modeling system(CMS)for generating the dataset to train and validate the proposed AIbased models.Second,three AI approaches namely:Support Vector Regression(SVR),Gaussian Process Regression(GPR),and Artificial Neural Networks(ANN)were developed to predict sedimentation quantities.Third,a comparison between the developed models was conducted using quality assessment criteria to evaluate their performance and choose the best one.Fourth,a sensitivity analysis was performed to provide insights into the factors affecting sedimentation.Lastly,a decision support tool was developed to predict harbors’sedimentation quantities.Results showed that the ANN model outperforms other models with mean absolute percentage error(MAPE)equals 4%.Furthermore,sensitivity analysis demonstrated that the main breakwater inclination angle,porosity,and harbor basin width affect significantly sediment transport.This research makes a significant contribution to the management of coastal structures by developing an AI data-driven framework that is beneficial for harbors’authorities.Ultimately,the developed decision-support AI tool could be used to predict harbors’sedimentation quantities in an easy,cheap,accurate,and practical manner compared to physical modeling which is time-consuming and costly.
文摘Beach groynes are structures for erosion protection along sandy coasts near inlets and can reduce the coastal erosion substantially,but open groynes cannot stop erosion completely because sand can be removed from the groyne compartments by cross-shore processes.Beach groynes should be designed with sufficient bypassing of sand to minimise erosion.Regular beach maintenance is required to keep a sufficient beach width for recreational purposes.The effectiveness of groyne compartments can be significantly improved by using T-head groynes or by using a submerged sill or breakwater in between the groynes.An economic evaluation shows that the beach maintenance costs over 50 years may be substantially higher than the construction costs of a submerged breakwater.An important parameter to be studied is the longshore transport,which requires detailed information of the wave climate,preferably based on measured data(offshore buoys)in combination with deep water wave modelling.Various models have been used to determine the net longshore sand transport and coastline changes.The design of groynes to reduce coastal erosion is illustrated by three field cases(Atlantic coast near Soulac,France;Lagos coast,Nigeria and Black Sea coast,Romania).These example cases show that beach groynes are effective structures,but sufficient bypassing of longshore sand transport is essential to minimise erosion.Regular beach fills in the groyne compartments may be required at high-energy(exposed)coasts.A submerged or emerged breakwater can be built between the groynes to protect the beach in the groyne compartments against erosion by cross-shore processes.
基金supported by the National Natural Science Foundation of China (Grant No. 50779010)
文摘A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.
基金supported by the National Natural Science Foundation of China (Grant No. 51179065)the National Science and Technology Support Plan (Grant No. 2012BAB03B02)
文摘Flat geotubes are widely used for coastal structures such as seawalls, breakwaters and sightseeing groins, etc.. However, the understanding of the stable mechanism involved in the wave-structure interactions should be deepened, and one of the important work is to clarify the stress state of the structure under the wave action. In this article, wave force acting on coastal structures made of flat geotube is experimentally investigated. The required drag, inertia and lift coefficients are especially analyzed from the results of hydraulic model experiments specially designed for geotube structure. Several types of structures made of flat geotubes under wave action have been tested in order to understand the stress state of the geotube fixed to force transducer within different structures. Experimental results show that the wave-induced forces on the instrumented geotube are markedly influenced by wave elements. Meanwhile, the magnitude of horizontal force of adjoining geotube is different at the same time.
文摘Numerical analysis was made for shoreline evolution in the vicinity ofcoastal structures, including spur dike, detached breakwaters. The nonlinear partial differentialequation was derived, and numerical solutions were obtained by the finite difference method. Thenumerical results show good agreement with previous analytical results.
基金supported by the National Natural Science Foundation of China(Grant No. 50779014)
文摘The interaction between solid structures and free-surface flows is investigated in this study. A Smoothed Particle Hy- drodynamics （SPH） model is used in the investigation and is verified against analytical solutions and experimental obser- vations. The main aim is to examine the effectiveness of a tsunami-resistant house design by predicting the wave loads on it. To achieve this, the solitary wave generation and ran-up are studied first. The solitary wave is generated by allowing a heavily weighted block to penetrate into a tank of water at one end, and the near-shore seabed is modelled by an inclined section with a constant slope. Then, the SPH model is applied to simulate the three-dimensional flows around different types of houses under the action of a solitary wave. It has been found that the tsunami-resistant house design reduces the impact force by a factor of three.
文摘This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is represented by acoustic type, potential based fluid elements. The elasto-plastic behavior of the soil medium is idealized using Drucker-Prager yield criterion based on associated flow rule assumption. Four nodded plane strain elements are used to model the concrete wall, foundation, subsoil, backfill and seabed zones. Fluid Structure Interface （FSI） elements are considered between the seawater interfaces with the quay-wall and the seabed. Frictional contact elements are employed between the wall and soil interfaces. The numerical model is validated using field measurements available for permanent drifts in a quay-wall damaged during Kobe earthquake. Reasonable agreements are obtained between the model predictions and the field measurements. Non-linear seismic analyses of the selected quay-wall subjected to both near-fault and far-fault ground motions are performed. An incremental dynamic analysis approach （IDA） is used. In general, at least for models examined in the current study, the gravity quay-walls are found to be more vulnerable to near-field, in comparison with the corresponding far-field, earthquakes.
基金The National Natural Science Foundation of China under contract Nos 41176102 and 41306116
文摘A fouling study was conducted in coastal waters southwest of the East China Sea between December 2013 and November 2014. A total of 84 species of fouling organisms belonging to 69 genera, 49 families, and 10 phyla were recorded over the entire year. The community composition was dominated by coastal warm-water species belonging to typical subtropical inner bay communities. The prosperous stage of settlement lasted from April to September, and the adhesion strength of the fouling organisms was the highest in summer. Sessile suspension feeders constituted the main core of settlement for the fouling community. Amphibalanus reticulatus was the most dominant and representative species of fouling organism, and other dominant species included Caprella equilibra, Ectopleura crocea, Anthopleura nigrescens, Stylochus ijimai, Spirobranchus kraussii, Crassostrea angulata, Perna viridis, Jassa falcata, Stenothoe valida, Sphaerozius nitidus, and Biflustra grandicella. The individuals in the fouling community showed a mutual dependence or constraint relationship due to competition for settlement space and food, and they exhibited a particular spatiotemporal distribution in accordance with adaptation to environmental factors. Temperature was the most important environmental factor determining the geographic distribution of fouling organisms. The temperature characteristics of species essentially reflect the differences in the fouling community composition in various climate zones. The species number, settlement stage, and settlement rate of fouling organisms are closely related to water temperature. Local natural environmental conditions（salinity, water currents, light, etc.） as well as human activity（such as aquaculture production） are all important factors affecting the settlement of fouling organisms.
基金This project was financially supported by the BK21 Division for U-CITY Construction,Sungkyunkwan University,Korea
文摘The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave overtopping of Nampo dike by use of Owen model, Van der Meer ＆ Janssen model and Hedges ＆ Reis model for wave overtopping of seawall. Based on the available tidal and wave data for storm surges in 1989, the risk assessment of wave overtopping of the Nampo dike has been carried out by both Level Ⅱ and Level Ⅲ reliability methods. The calculated resuhs show the general agreement of failure probability between the two methods. By utilizing the rehabilitated cross section of Nampo dike, the failure probability of wave overtopping for the Nampo dike after rehabilitation will be rapidly reduced to that of initial design at crest level of 9.0 m with the improved slope from 1 ： 2 to 1 ： 4 at seaside. Since the sea level may only rise 1.0 m in the next few decades, the failure probability of Nampo dike will be still in the safe range.
文摘The interactions between regular surface waves and a surface-pitching slotted barrier are investigated both analytically and experimentally. A quasi-linear theory is developed using the eigenfunction expansion method. The energy dissipation within the barriers is modeled by a quadratic friction factor, and an equivalent linear dissipation coefficient, which is depth-varying, wave-height dependent, is introduced to linearize the matching condition at the surface-pitching barrier. By comparing the theoretical results with laboratory experiments, it is shown that the present method can satisfactorily predict the variation of the reflection and transmission coefficients with wave height.
基金Project supported by the National Natural Science Foundation of China (Grant No: 50379026)
文摘A linear hybrid model of Mild Slope Equation （MSE） and Boundary Element Method （BEM） is developed to study the wave propagation around floating structures in coastal zones. Both the wave refraction under the influence of topography and the wave diffraction by floating structures are considered. Hence, the model provides wave properties around the coastal floating structures of arbitrary shape but also the wave forces on and the hydrodynamic characteristics of the structures. Different approaches are compared to demonstrate the validity of the present hybrid model. Several numerical tests are carried out for the cases of pontoons under different circumstances. The results show that the influence of topography on the hydrodynamic characteristics of floating structures in coastal regions is important and must not be ignored in the most wave period range with practical interests.
文摘The objective of this study is to develop a procedure to analyze the motions of a floating pier comprised of several pontoons that are modeled as rigid bodies and connected to each other by flexible and rigid connectors.Recently,the use of floating piers has increased because of their advantages,such as faster and higher-quality construction,seismic force isolation for a full-scale mooring system,low dependence on local soil conditions and tides,ability to relocate or reconfigure the pier modules during the operation period and 75-100 years of repair-free service.A floating pier consists of a pier,access bridge,mooring system and fender system,each of which comes in many variations to suit different usages and construction considerations.The typical loads used in the design of these piers are dead loads,live loads,mooring loads,fender loads and environmental loads induced by wind,currents and waves.For numerical simulation,three types of piers are used:passenger piers,light-cargo piers and semi-heavy-cargo piers.The selected piers consist of several large pontoons joined by pivots and have a pile-based mooring system.These piers are modeled by SAP2000software as two-dimensional frames that are linked together.As the first step,each type of pier is subjected to loading,and its general behavior is assessed.According to this behavior,the major load combinations are described for the design of piers and analyzed to determine the behavior of the modules.Lastly,according to the analysis results and the safe use and stability considerations,such as the maximum draft and longitudinal gradient,the dimensions of each module in each pier type are presented.
