The dynamic response behaviors of upright breakwaters under broken wave impact are analysed based on the mass-damper-spring dynamic system model. The effects of the mass, damping, stiffness, natural period, and impuls...The dynamic response behaviors of upright breakwaters under broken wave impact are analysed based on the mass-damper-spring dynamic system model. The effects of the mass, damping, stiffness, natural period, and impulse duration (or oscillation period) on the translation, rotation, sliding force, overturning moment, and corresponding dynamic amplifying factors are studied. It is concluded that the ampli-ying factors only depend on the ratio of the system natural period to impulse duration (or oscillation period) under a certain damping ratio. Moreover, the equivalent static approach to breakwater design is also discussed.展开更多
In order to suit the condition that the wave uplift is correlated with the horizontal wave load acting on a vertical breakwater, a generally used method for determining the reliability index β of the breakwater, i.e....In order to suit the condition that the wave uplift is correlated with the horizontal wave load acting on a vertical breakwater, a generally used method for determining the reliability index β of the breakwater, i.e. the Hasofer-Lind method, is extended in a generalized stochastic space for correlative variables. The computational results for a caisson breakwater indicate that the value of β for the case of correlated variables is obviously smaller than that for the case of independent variables.展开更多
Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation cou...Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.展开更多
It is assumed that, during the design period, the waves acting on breakwaters are divided into three types： standing wave, broken wave and breaking wave,and the wave heights fit the Rayleigh distribution while the wa...It is assumed that, during the design period, the waves acting on breakwaters are divided into three types： standing wave, broken wave and breaking wave,and the wave heights fit the Rayleigh distribution while the water depths, wave periods and duration of breaking wave impact force fit normal distribution. Based on the random samples of water depths, wave heights, wave periods and duration of breaking wave impact force, the types of waves acting on breakwaters are distinguished and the time-history model of the wave force is determined. The motions of caisson breakwaters under the wave force are simulated by a dynamic numerical model and the statistic characteristics of the dynamic responses are analyzed with the Monte Carlo method. A probabilistic procedure to analyze the motion of the breakwater is developed therein. The procedure is illustrated by an example.展开更多
设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合...设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合结构工作性能的影响,采用气室内波幅放大系数、气室顶部空气点压力和防波堤前波浪反射率作为考察参量。展开更多
The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding and vibrating- rocking motions. The models of vibrating motion and vibrating-sliding motion have been pro...The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding and vibrating- rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an early paper. In this paper, a model of vibrating- rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated, In case the overturning moment exceeds the stability moment of a caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle, It is shown that the sliding force and overturning moment of breakwaters can be reduced effectively due to the rocking motion, It is proposed that some rocking motion should be allowed in breakwater design.展开更多
A new method of treating maximum wave height as a random variable in reliability analysis of breakwater caissons isproposed. The maximum wave height is expressed as the significant wave height multiplied by the so-cal...A new method of treating maximum wave height as a random variable in reliability analysis of breakwater caissons isproposed. The maximum wave height is expressed as the significant wave height multiplied by the so-called wave height ratio.The proposed wave height ratio is a type of transfer function from the significant wave height to the maximum wave height.Under the condition of a breaking wave, the ratio is intrinsically nonlinear. Therefore, the probability density function for thevariable cannot be easily defined. In this study, however, it can be derived from the relationship between the maximum andsignificant waves in a nonbreaking environment. Some examples are shown to validate the derived probability density functionfor the wave ratio parameter. By introducing the wave height ratio into reliability analysis of caisson breakwater, the maximumwave height can be used as an independent and primary random variable, which means that the risk of caisson failure during itslifetime can be evaluated realistically.展开更多
The quarter-circular caisson breakwater （QCB） is a new type of breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be le...The quarter-circular caisson breakwater （QCB） is a new type of breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be less than that of semi-circular breakwaters in deepwater. In order to study the wave force distribution acting on the QCB, to find wave force formula for this type of breakwater, firstly in this paper, the distribution characteristics of the horizontal force, the downward vertical force and the uplift force on the breakwater were gotten based on physical model wave flume experiments and on the analysis of the wave pressure experimental data. Based on a series of physical model tests acted by irregular waves, a kind of calculation method, which was modified by Goda formula, was proposed to carry out the wave force on the QCB. Secondly, the reliability method with correlated variables was adopted to analyze the QCB, considering the high correlation between wave forces or moments. Utilizing the observed wave data in engineering field, the reliability index and failure probability of QCB were obtained. Finally, a factor Q=0.9 is given to modify the zero pressure height above SWL of QCB, and wave force partial coefficient 1.34 to the design expressions of QCB for anti-sliding, as well as 1.67 for anti-overturning, were presented.展开更多
The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they...The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures.Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor,a new perforated caisson of breakwater is designed in this paper.The ordinary caisson is modified by installing facilities similar to the air chamber of OWC converter,but here they are utilized to dissipate the wave energy inside the caisson.Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber.This innovation has both academic significance and important engineering value.For a new type of caisson,reliability analysis of the structure is necessary.Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson.The calculated results are compared with experimental data,showing the feasibility of the method.The Importance Sampling Procedure(ISP) is used to analyse the reliability of this caisson breakwater.展开更多
The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical mo...The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical modelling was conducted using FLOW-3 D software.In this study,the wave overtopping from composite berm breakwater as new conceptual structure and the pressure imposed on the composite berm breakwater are considered and investigated.The results show a decrease of 84.01,70.88 and 61.42 percent of the wave overtopping in the composite berm breakwater,in comparison to the rubble mound breakwater,horizontally caisson breakwater and caisson breakwater,respectively.Also,the pressure applied to the composite berm breakwater with the pressure applied to the horizontally caisson breakwater was compared and evaluated.Composite berm breakwater compared with horizontally caisson breakwater in P1,the amount of the obtained pressure decreased by 52.09%,in P2 the amount of the obtained pressure decreased by 63.07%,in P3 decreased by 76.09%and in Pu,this pressure reduced by53.92%.For the composite berm breakwater,the impact of three types of berms,homogenous berm(Type 1),a berm consisting of armor-filter(Type 2)and multi-layer berm(Type 3)with the aim of optimizing the hydraulic responses and wave interaction on the caisson of the breakwater was examined and evaluated.In total,Type 3 will be recommended with a significant reduction in the overtopping values and maximum pressure.展开更多
-The construction of breakwaters in China in more than 40 years since the founding of the People's Republic of China is reviewed. The construction of two main types of breakwater, upright breakwaters and rubble mo...-The construction of breakwaters in China in more than 40 years since the founding of the People's Republic of China is reviewed. The construction of two main types of breakwater, upright breakwaters and rubble mound breakwaters, and the way in which they are built are expounded. Recommendations to improve the technology for future breakwater construction are presented.展开更多
首次将随机波浪荷载应用于矩形沉箱防波堤的动力分析,并将其动力运动过程分为:摇摆、摇摆-滑移运动两种运动模态,同时引入了侧向阻滑板-转角弹簧-阻尼器和阻滑板-竖向弹簧-阻尼器两种模型体系,建立了相应的动力计算模型,推导出了各运动...首次将随机波浪荷载应用于矩形沉箱防波堤的动力分析,并将其动力运动过程分为:摇摆、摇摆-滑移运动两种运动模态,同时引入了侧向阻滑板-转角弹簧-阻尼器和阻滑板-竖向弹簧-阻尼器两种模型体系,建立了相应的动力计算模型,推导出了各运动模态的动力方程,并分别采用Fortran语言编译的程序和有限元软件AN SY S对两种模型进行实施。通过实例的计算分析表明,两种模型和方法均可有效地对随机波浪作用下沉箱防波堤动力响应进行数值模拟,而后者更符合实际受力情况,精度更高。展开更多
文摘The dynamic response behaviors of upright breakwaters under broken wave impact are analysed based on the mass-damper-spring dynamic system model. The effects of the mass, damping, stiffness, natural period, and impulse duration (or oscillation period) on the translation, rotation, sliding force, overturning moment, and corresponding dynamic amplifying factors are studied. It is concluded that the ampli-ying factors only depend on the ratio of the system natural period to impulse duration (or oscillation period) under a certain damping ratio. Moreover, the equivalent static approach to breakwater design is also discussed.
文摘In order to suit the condition that the wave uplift is correlated with the horizontal wave load acting on a vertical breakwater, a generally used method for determining the reliability index β of the breakwater, i.e. the Hasofer-Lind method, is extended in a generalized stochastic space for correlative variables. The computational results for a caisson breakwater indicate that the value of β for the case of correlated variables is obviously smaller than that for the case of independent variables.
基金supported by the National Natural Science Foundation of China(Grant No.50979069)the Science and Technology Project of West China Traffic Construction(Grant No.200632800003-06)
文摘Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.
基金This studyis supported bythe National Natural Science Foundation of China (Grant No.50579046) the ScienceFoundation of Tianjin Municipal Commission of Science and Technology (Grant No.043114711)
文摘It is assumed that, during the design period, the waves acting on breakwaters are divided into three types： standing wave, broken wave and breaking wave,and the wave heights fit the Rayleigh distribution while the water depths, wave periods and duration of breaking wave impact force fit normal distribution. Based on the random samples of water depths, wave heights, wave periods and duration of breaking wave impact force, the types of waves acting on breakwaters are distinguished and the time-history model of the wave force is determined. The motions of caisson breakwaters under the wave force are simulated by a dynamic numerical model and the statistic characteristics of the dynamic responses are analyzed with the Monte Carlo method. A probabilistic procedure to analyze the motion of the breakwater is developed therein. The procedure is illustrated by an example.
文摘设计一种带收缩水道的沉箱防波堤和OWC(Oscillating Water Column)波能发电装置相结合的复合结构形式,开展物理模型试验研究。通过改变水道结构形式与OWC气室参数,并分析实验数据,探讨水道形式、入射波要素和OWC气室形状参数等对该复合结构工作性能的影响,采用气室内波幅放大系数、气室顶部空气点压力和防波堤前波浪反射率作为考察参量。
基金Extended work of the project"Dynamic Responses of Composite Breakwaters to Breaking Wave Impact"financially supported by the Ministry of Transport Exchange Fund,Japan
文摘The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding and vibrating- rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an early paper. In this paper, a model of vibrating- rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated, In case the overturning moment exceeds the stability moment of a caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle, It is shown that the sliding force and overturning moment of breakwaters can be reduced effectively due to the rocking motion, It is proposed that some rocking motion should be allowed in breakwater design.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea Government Ministry of Knowledge Economy(Grant No.20123030020110)
文摘A new method of treating maximum wave height as a random variable in reliability analysis of breakwater caissons isproposed. The maximum wave height is expressed as the significant wave height multiplied by the so-called wave height ratio.The proposed wave height ratio is a type of transfer function from the significant wave height to the maximum wave height.Under the condition of a breaking wave, the ratio is intrinsically nonlinear. Therefore, the probability density function for thevariable cannot be easily defined. In this study, however, it can be derived from the relationship between the maximum andsignificant waves in a nonbreaking environment. Some examples are shown to validate the derived probability density functionfor the wave ratio parameter. By introducing the wave height ratio into reliability analysis of caisson breakwater, the maximumwave height can be used as an independent and primary random variable, which means that the risk of caisson failure during itslifetime can be evaluated realistically.
基金Supported by the Natural Science Foundation of Hebei Province （Grant No. E2012201057） the Scientific and Technological Projects of Hebei Province （Grant No. 2009056） the Natural Science Foundation of Tianjin （Grant No. 10JCYBJC03700）
文摘The quarter-circular caisson breakwater （QCB） is a new type of breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be less than that of semi-circular breakwaters in deepwater. In order to study the wave force distribution acting on the QCB, to find wave force formula for this type of breakwater, firstly in this paper, the distribution characteristics of the horizontal force, the downward vertical force and the uplift force on the breakwater were gotten based on physical model wave flume experiments and on the analysis of the wave pressure experimental data. Based on a series of physical model tests acted by irregular waves, a kind of calculation method, which was modified by Goda formula, was proposed to carry out the wave force on the QCB. Secondly, the reliability method with correlated variables was adopted to analyze the QCB, considering the high correlation between wave forces or moments. Utilizing the observed wave data in engineering field, the reliability index and failure probability of QCB were obtained. Finally, a factor Q=0.9 is given to modify the zero pressure height above SWL of QCB, and wave force partial coefficient 1.34 to the design expressions of QCB for anti-sliding, as well as 1.67 for anti-overturning, were presented.
基金supported by the National Natural Science Foundation of China (Grant No 4087-6047)
文摘The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures.Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor,a new perforated caisson of breakwater is designed in this paper.The ordinary caisson is modified by installing facilities similar to the air chamber of OWC converter,but here they are utilized to dissipate the wave energy inside the caisson.Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber.This innovation has both academic significance and important engineering value.For a new type of caisson,reliability analysis of the structure is necessary.Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson.The calculated results are compared with experimental data,showing the feasibility of the method.The Importance Sampling Procedure(ISP) is used to analyse the reliability of this caisson breakwater.
文摘The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical modelling was conducted using FLOW-3 D software.In this study,the wave overtopping from composite berm breakwater as new conceptual structure and the pressure imposed on the composite berm breakwater are considered and investigated.The results show a decrease of 84.01,70.88 and 61.42 percent of the wave overtopping in the composite berm breakwater,in comparison to the rubble mound breakwater,horizontally caisson breakwater and caisson breakwater,respectively.Also,the pressure applied to the composite berm breakwater with the pressure applied to the horizontally caisson breakwater was compared and evaluated.Composite berm breakwater compared with horizontally caisson breakwater in P1,the amount of the obtained pressure decreased by 52.09%,in P2 the amount of the obtained pressure decreased by 63.07%,in P3 decreased by 76.09%and in Pu,this pressure reduced by53.92%.For the composite berm breakwater,the impact of three types of berms,homogenous berm(Type 1),a berm consisting of armor-filter(Type 2)and multi-layer berm(Type 3)with the aim of optimizing the hydraulic responses and wave interaction on the caisson of the breakwater was examined and evaluated.In total,Type 3 will be recommended with a significant reduction in the overtopping values and maximum pressure.
文摘-The construction of breakwaters in China in more than 40 years since the founding of the People's Republic of China is reviewed. The construction of two main types of breakwater, upright breakwaters and rubble mound breakwaters, and the way in which they are built are expounded. Recommendations to improve the technology for future breakwater construction are presented.
文摘首次将随机波浪荷载应用于矩形沉箱防波堤的动力分析,并将其动力运动过程分为:摇摆、摇摆-滑移运动两种运动模态,同时引入了侧向阻滑板-转角弹簧-阻尼器和阻滑板-竖向弹簧-阻尼器两种模型体系,建立了相应的动力计算模型,推导出了各运动模态的动力方程,并分别采用Fortran语言编译的程序和有限元软件AN SY S对两种模型进行实施。通过实例的计算分析表明,两种模型和方法均可有效地对随机波浪作用下沉箱防波堤动力响应进行数值模拟,而后者更符合实际受力情况,精度更高。
