Vibrating-Rocking Motion of Caisson Breakwater Under Breaking Wave Impact

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.

Vibrating-Sliding Motion of Caisson Breakwaters Under Various Breaking Wave Impact Forces

Sliding is one of the principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. Herein, the mass-spring-dashpot model of caisson-base system is used to simulate the vibrating-sliding motion of the caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave impacts and the sliding motion on the dynamic response behaviors of caisson breakwaters are investigated and the calculation of relevant system parameters is discussed. It is shown that the dynamic responses of the caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. The amplitude of dynamic response of the caisson is lower under single peak impact excitation than that under double peak impact or shock-damping oscillation impact excitation. Though the displacement of the caisson is large due to sliding, the rotation, the sliding force and the overturning moment of the caisson are significantly reduced.

VIBRATING-UPLIFT ROCKING MOTION OF CAISSONBREAKWATERS UNDER VARIOUS BREAKINGWAVE IMPACT FORCES

Overturning is one of principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. The mass-spring-dashpot model of caisson-foundation system is used to simulate the vibrating-uplift rocking motion of caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave types and the uplift rocking motion on dynamic response behaviors of caisson breakwaters are investigated. It is shown that the dynamic responses of a caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. Though the rotation of a caisson is larger due to the uplift rocking motion, the displacement, the sliding force and the overturning moment of the caisson are significantly reduced. It provides the theoretical base for the design idea that the uplift rocking motion of caisson is allowed in design.

直立防波堤振动──滑移运动分析的模型和方法

建立了一个动力系统模型及相应分析方法，对破碎波冲击作用下直立式防波堤的振动—滑移运动过程进行数值模拟，预测特殊波浪力作用下防波堤可能出现的滑移量。用本文模型和方法对一沉箱防波堤在破碎波作用下的运动过程进行了计算，并分析了沿基床顶面的滑移对沉箱位移、摇摆角、滑移力和倾覆力矩的影响。

破碎波冲击作用下沉箱式防波堤振动-摇摆运动分析

文中建立了沉箱式防波堤弹性振动 -摇摆运动分析模型 ,可对破碎冲击作用下防波堤的弹性振动 -摇摆运动过程进行数值摸拟。研究了摇摆运动对防波堤位移、转角、滑移力和倾覆力距的影响。结果表明 ,当倾覆力距大于防波堤的稳定力矩时 ,防波堤并不一定发生倾倒破坏 ;只有当防波堤摇摆运动转角大于倾倒的临界角时 ,防波堤才会发生倾倒破坏。而且摇摆运动可有效减小防波堤的滑移力和倾覆力矩。故在极限设计破碎波浪条件下可考虑允许防波堤出现摇摆运动 ,以实现更为经济的结构设计。

近破波作用下沉箱式防波堤运动特性的模型实验研究

对近破波作用下沉箱式防波堤的运动特性进行了模型实验研究。实验中测量了沉箱模型与基床的摩擦系数、基床刚度和阻尼系数;不同水位情况下作用于沉箱模型上的近破波波压力时程;近破波作用下沉箱模型的位移和转角响应时程等,并与数学模型计算结果进行了比较分析。实验结果表明,若沉箱的滑移力大于沉箱与基床间的摩擦力,在连续波浪作用下,沉箱将连续出现间歇式滑移运动,数学模型可较好地模拟这一运动过程。

不同类型近破波作用下沉箱式防波堤的振动-提离摇摆运动

倾覆失稳是沉箱式防波堤的主要破坏形式之一,是稳定性验算的基本内容· 采用质量_弹簧_阻尼器集总参数模型模拟沉箱式防波堤在单峰值冲击型、双峰值冲击型和冲击_振荡衰减型等不同类型近破波作用下的振动_提离摇摆运动过程,研究了不同类型近破波和沉箱的提离摇摆运动对沉箱式防波堤动力响应的影响· 结果表明,在近破波冲击力幅值相同的条件下,近破波类型对沉箱的动力响应影响很大;提离摇摆运动虽然会使沉箱的转角幅值增大,但可有效地减小沉箱的位移。

沉箱式防波堤振动——摇摆运动分析的模型和方法

建立了沉箱式防波堤弹性振动—摇摆运动分析模型 ,对破碎波冲击作用下防波堤的弹性振动——摇摆运动过程进行了数值模拟 ,并研究了摇摆运动对防波堤位移、转角、滑移力和倾覆力矩的影响。结果表明 ,摇摆运动可有效减小防波堤的的滑移力和倾覆力矩。在防波堤设计中可考虑允许出现摇摆运动 。