Evaluation of wave impact loads on caisson breakwaters based on joint probability of impact maxima and rise times

Abstract

When waves break against seawalls, vertical breakwaters , piers or jetties, they abruptly transfer their momentum into the structure. This energy transfer is always spectacular and perpetually unrepeatable but can also be very violent and affect the stability and the integrity of coastal structures. Over the last 15 years, increasing awareness of wave-impact induced structural failures of maritime structures has emphasised the need for a more complete approach to dynamic responses, including effects of impulsive loads. At the same time, movement of design standards toward probabilistic approaches requires new statistical tools able to account for uncertainties in the variability of wave loading processes. This paper presents a new approach to the definition of loads for use in performance design of vertical coastal structures subject to breaking wave impacts. Based on conservation of momentum and joint probability of non-dimensional wave impact maxima and rise times from large-scale test measurements, a new set of equations have been derived to characterise design impact loads at different non-exceedance probability levels and guidance is given for the estimation of the static-equivalent design loads to be used in early-stage feasibility studies. Predictions of static equivalent design loads and corresponding safety factor against sliding using the proposed methodology are found to be in very good agreement with both predictions by most established deterministic methods and field observations reported in literature.

Overtopping Flow Impact on a Vertical Wall on a Dike Crest

“…The definition of t r can be referred to Fig.2 from Cuomo et al (2011). Most of the researchers have been reported that there is a relationship between P im and t r :…”

“…Based on the concept of constant impulse during the wave impact, a relation between maximum impact pressure P im and impact rising time t r can be built (e.g., Weggel and Maxwell;Salih Kirkgöz, 1990;Hattori et al, 1994;Cuomo et al, 2011;Ariyarathne et al, 2012). The definition of t r can be referred to Fig.2 from Cuomo et al (2011).…”

Dynamic magnification response of a vertical plate exposed to breaking wave impact

“…Plate deflection, w, can be found by solving equation (1), using the boundary and initial conditions defined by equations (4)- (6). The bending moments M x and M y can be determined from equations (2) and (3) using the values of w.…”

“…The experimental data of model and prototype tests on the interaction of coastal structures and waves show that high-magnitude impact (shock) pressures are formed when waves break directly on seawalls which are vertical faced. [1][2][3][4][5][6][7][8][9][10][11][12] From the past investigations, [13][14][15] the spatial distribution of impact pressures on the wave-structure interface has become quite well known. There are various dynamic analysis on the spatial and temporal distribution of wave loading on structures using some numerical models; [16][17][18][19][20][21] however, especially in engineering practice, it is more convenient to follow a method which is based on static analyses.…”

Characterisation of Breaking Waves on the Eddystone Lighthouse: A Laboratory Investigation on Wave Pressure

“…characterised by small breaking distances or low aeration levels. In addition, it is generally accepted that the impulsivity tends to decrease with the increase in the breaking distance and the aeration effect results in a cushioning effect (visible with a pressure oscillation), which tends to damp the pressure peak and to increase the impact duration (Oumeraci et al 1993;Hattori et al 1994;Hull and Muller 2002;Bredmose et al 2009;Cuomo et al 2011). Typically, broken waves exhibit much smaller pressures than plunging impacts.…”