Caisson Breakwater Analysis

1) Review of Existing Models for Dynamics of Caisson Breakwaters

The model proposed by Oumeraci and Kortenhaus (1994) represents, despite of its relative simplicity, an efficient tool for the determination of the dynamic response of caisson breakwaters to wave impact loads and done a good effort to quantify the importance of the applied dynamic load and dynamic properties of the breakwater (including the superstructure, its foundation, soil and the surrounding water). It is modeled as a 2-DOF (figure- 1) in an idealized 2D lumped system, horizontal translation and rotation around A.

2) Review of Existing Time-history Wave Loads on Caisson Breakwaters

Generally, the impact load for dynamic calculation is idealized by a triangular impulsive

Form this concern, a non-linear model is proposed by Lupoi et al (2007) that allows accounting for wave-structure-soil interaction and evaluate the dynamic response of caisson breakwater subjected to impulsive wave loads, but is also fast and accurate enough to be used in design of caisson breakwaters. The caisson (figure- 3) is represented by a rigid block sitting on a mattress of non-linear springs. The caisson transfers horizontal and vertical forces to the foundation soil when a wave hits the superstructure. The structure is modeled as a 3-DOF, two translation and one rotation. The dynamic properties of the system include contributions by the superstructure, water surrounding the structure and the soil

By performing numerical calculations, it is observed that 10% variation in mass may already affect the dynamic response. The stiffness terms also belong to the parameters which could not properly evaluated, keeping all the parameters constant it is shown that, a variation of 10% stiffness may already affect the dynamic response. Variation of the damping terms almost does not have any effect on the period of oscillations and maximum amplitude of the response (first cycle). On the other hand, damping strongly affects the magnitude of the amplitudes of oscillations after the first cycle. 5.2) Breaking Wave Time-history Loads

Cuomo, Lupoi, Shimosako and Takahashi (2011) found that breaking wave impact pressures might well exceed those expected by most established prediction methods and suggested a new set of formula for impulsive loading. Several attempts have been made to define a functional relation between wave impact maxima and rise time (Cuomo; 2005). A simplified procedure of the formulations thus insured consistency between generated wave impact maxima and rise time. 5.3) Dynamic Motion of the Caisson