Motion and stability of caisson breakwaters under breaking wave impact

2001 ◽  
Vol 28 (6) ◽  
pp. 960-968 ◽  
Author(s):  
Y -Z Wang
Keyword(s):  
Dynamic Characteristics ◽  
Wave Force ◽  
Breaking Wave ◽  
Wave Impact ◽  
Sliding Motion ◽  
Rocking Motion ◽  
Overturning Moment ◽  
The Stability ◽  
Caisson Breakwater ◽  
Sliding Force

The possible motions of caisson breakwaters under dynamic load excitation include vibrating motion, vibrating–sliding motion, and vibrating–rocking motion. Three models are presented in this paper and are used to simulate the histories of vibrating–sliding–rocking motions of caissons under breaking wave impact. The effect of the dynamic characteristics of the caisson–foundation system and the motions on the displacement, rotation, sliding force, and overturning moment of caissons are investigated. It is shown that the sliding force of the caisson is different from the breaking wave force directly acting on the caisson due to the motion of the caisson and the sliding motion or rocking motion of the caisson can limit the sliding force or overturning moment of the caisson to a certain value. The sliding force never exceeds the friction force between the caisson and the foundation, and the overturning moment never exceeds the stability moment of the caisson. It is concluded that the wave conditions, the dynamic characteristics, and the motions of the caisson–foundation system should be considered in design.Key words: caisson breakwater, breaking wave, vibrating, sliding, rocking.

Vibrating-uplift rocking motion of caisson breakwaters under various breaking wave impact forces

2005 ◽  
Vol 26 (5) ◽  
pp. 579-586
Author(s):  
Wang Yuan-zhan ◽  
Zhou Zhi-rong ◽  
Yang Hai-dong
Keyword(s):  
Breaking Wave ◽  
Wave Impact ◽  
Impact Forces ◽  
Rocking Motion

The Distribution of Breaking and Non-Breaking Wave Impact Forces

2009 ◽  
Author(s):  
Anne M. Fullerton ◽  
Ann Marie Powers ◽  
Don C. Walker ◽  
Susan Brewton
Keyword(s):  
Breaking Wave ◽  
Wave Impact ◽  
Impact Forces

scholarly journals Characteristics of Breaking Wave Forces on Piles over a Permeable Seabed

2021 ◽  
Vol 9 (5) ◽  
pp. 520
Author(s):  
Zhenyu Liu ◽  
Zhen Guo ◽  
Yuzhe Dou ◽  
Fanyu Zeng
Keyword(s):  
Wave Breaking ◽  
Stokes Equations ◽  
Slope Angle ◽  
Wave Force ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Secondary Wave ◽  
Wave Forces ◽  
Breaking Wave ◽  
Breaking Wave Forces

Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.

scholarly journals Influence of the Spatial Pressure Distribution of Breaking Wave Loading on the Dynamic Response of Wolf Rock Lighthouse

2021 ◽  
Vol 9 (1) ◽  
pp. 55
Author(s):  
Darshana T. Dassanayake ◽  
Alessandro Antonini ◽  
Athanasios Pappas ◽  
Alison Raby ◽  
James Mark William Brownjohn ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Pressure Distribution ◽  
Distinct Element ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Wave Loading ◽  
Wave Impact ◽  
Pressure Distributions ◽  
Impact Area ◽  
The Impact

The survivability analysis of offshore rock lighthouses requires several assumptions of the pressure distribution due to the breaking wave loading (Raby et al. (2019), Antonini et al. (2019). Due to the peculiar bathymetries and topographies of rock pinnacles, there is no dedicated formula to properly quantify the loads induced by the breaking waves on offshore rock lighthouses. Wienke’s formula (Wienke and Oumeraci (2005) was used in this study to estimate the loads, even though it was not derived for breaking waves on offshore rock lighthouses, but rather for the breaking wave loading on offshore monopiles. However, a thorough sensitivity analysis of the effects of the assumed pressure distribution has never been performed. In this paper, by means of the Wolf Rock lighthouse distinct element model, we quantified the influence of the pressure distributions on the dynamic response of the lighthouse structure. Different pressure distributions were tested, while keeping the initial wave impact area and pressure integrated force unchanged, in order to quantify the effect of different pressure distribution patterns. The pressure distributions considered in this paper showed subtle differences in the overall dynamic structure responses; however, pressure distribution #3, based on published experimental data such as Tanimoto et al. (1986) and Zhou et al. (1991) gave the largest displacements. This scenario has a triangular pressure distribution with a peak at the centroid of the impact area, which then linearly decreases to zero at the top and bottom boundaries of the impact area. The azimuthal horizontal distribution was adopted from Wienke and Oumeraci’s work (2005). The main findings of this study will be of interest not only for the assessment of rock lighthouses but also for all the cylindrical structures built on rock pinnacles or rocky coastlines (with steep foreshore slopes) and exposed to harsh breaking wave loading.

Stabilization of networked switched affine systems with event-triggered strategy

2021 ◽  
pp. 014233122110213
Author(s):  
Dandan Li ◽  
Zhiqiang Zuo ◽  
Yijing Wang
Keyword(s):  
Affine Systems ◽  
Switching Law ◽  
Event Time ◽  
Sliding Motion ◽  
State Dependent ◽  
Event Triggering ◽  
Stability Issue ◽  
The Stability ◽  
Event Based ◽  
Selection Of

Using an event-based switching law, we address the stability issue for continuous-time switched affine systems in the network environment. The state-dependent switching law in terms of the region function is firstly developed. We combine the region function with the event-triggering mechanism to construct the switching law. This can provide more candidates for the selection of the next activated subsystem at each switching instant. As a result, it is possible for us to activate the appropriate subsystem to avoid the sliding motion. The Zeno behavior for the switched affine system can be naturally ruled out by guaranteeing a positive minimum inter-event time between two consecutive executions of the event-triggering threshold. Finally, two numerical examples are given to demonstrate the effectiveness of the proposed method.

Dynamic analysis and control of an active engine mount system

2002 ◽  
Vol 216 (11) ◽  
pp. 921-931 ◽  
Author(s):  
Y-W Lee ◽  
C-W Lee
Keyword(s):  
Transfer Function ◽  
Dynamic Characteristics ◽  
Performance Test ◽  
Adaptive Controller ◽  
Lms Algorithm ◽  
Equivalent Mass ◽  
Engine Mount ◽  
Active Engine ◽  
The Stability ◽  
Mass Spring

Dynamic characteristics of a prototype active engine mount (AEM), designed on the basis of a hydraulic engine mount, have been investigated and an adaptive controller for the AEM has been designed. An equivalent mass-spring-damper AEM model is proposed, and the transfer function that describes the dynamic characteristics of the AEM is deduced from mathematical analysis of the model. The damping coefficient of the model is derived by considering the non-linear flow effect in the inertia track. Experiments confirmed that the model precisely describes the dynamic characteristics of the AEM. An adaptive controller using the filtered-X LMS algorithm is designed to cancel the force transmitted through the AEM. The stability of the LMS algorithm is guaranteed by using the secondary path transfer function derived on the basis of the dynamic model of the AEM. The performance test in the laboratory shows that the AEM system is capable of significantly reducing the force transmitted through the AEM.

Sailing Yacht Capsizing

1981 ◽  
Author(s):  
Olin J. Stephens ◽  
Karl L. Kirkman ◽  
Robert S. Peterson
Keyword(s):  
Stability Analysis ◽  
Dynamic Mechanism ◽  
Focused Attention ◽  
Breaking Wave ◽  
Wave Impact ◽  
Single Wave ◽  
Loss Of Life ◽  
Classical Stability ◽  
Sailing Yacht

The 1979 Fastnet focused attention upon yacht capsizes and resulting damage and loss of life. A classical stability analysis does not clearly reveal some of the characteristics of the modern racing yacht which may exacerbate a capsizing tendency. A review of the mechanism of a single-wave-impact capsize reveals inadequacies in static methods of stability analysis and hints at a connection between recent design trends and an increased frequency of capsize. The paper traces recent design trends, relates these to capsizing by a description of the dynamic mechanism of breaking wave impact, and outlines the unusual oceanography of the 1979 Fastnet which led to a heightened incidence of capsize.

scholarly journals Wave Impact Loads on Vertical Seawalls: Effects of the Geometrical Properties of Recurve Retrofitting

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2849
Author(s):  
Shudi Dong ◽  
Md Salauddin ◽  
Soroush Abolfathi ◽  
Jonathan Pearson
Keyword(s):  
Impact Force ◽  
Vertical Wall ◽  
Impact Loads ◽  
Geometrical Shape ◽  
Wave Loading ◽  
Wave Impact ◽  
Static Loads ◽  
Geometrical Properties ◽  
Overhang Length ◽  
Overturning Moment

This study investigates the variation of wave impact loads with the geometrical configurations of recurve retrofits mounted on the crest of a vertical seawall. Physical model tests were undertaken in a wave flume at the University of Warwick to investigate the effects of the geometrical properties of recurve on the pressure distribution, overall force, and overturning moment at the seawall, subject to both impulsive and non-impulsive waves. Additionally, the wave impact and quasi-static loads on the recurve portion of the retrofitted seawalls are investigated to understand the role of retrofitting on the structural integrity of the vertical seawall. Detailed analysis of laboratory measurements is conducted to understand the effects of overhang length and height of the recurve wall on the wave loading. It is found that the increase in both recurve height and overhang length lead to the increase of horizontal impact force at an average ratio of 1.15 and 1.1 times larger the reference case of a plain vertical wall for the tested configurations. The results also show that the geometrical shape changes in recurve retrofits, increasing the overturning moment enacted by the wave impact force. A relatively significant increase in wave loading (both impact and quasi-static loads) are observed for the higher recurve retrofits, while changes in the overturning moment are limited for the retrofits with longer overhang length. The data generated from the physical modelling measurements presented in this study will be particularly helpful for a range of relevant stakeholders, including coastal engineers, infrastructure designers, and the local authorities in coastal regions. The results of this study can also enable scientists to design and develop robust decision support tools to evaluate the performance of vertical seawalls with recurve retrofitting.

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