Reliability Analysis Of Chamfered Vertical Breakwater

In recent years, the construction of breakwaters in deepwater has been moreprevalent while the coastal and ocean resources are developed and utilized. In deepsea area, the large waves generate tremendous wave forces acting on the breakwaters,and therefore, various new types of breakwaters have been proposed to reduce thoseforces. The chamfered breakwater is an improved type of vertical breakwater, thesuperstructure of which has a sloping surface on the seaward side. The anglebetween the slope and the horizontal plane is usually taken as an acute angle (such as30°, 45°). The wave crest force acting on the sloping surface of the superstructurecan be disintegrated into a horizontal component and a vertical downwardcomponent. The vertical component of the wave force is advantageous to thestability of the breakwater.In this paper, the researches on the chamfered vertical breakwater are carriedout in both theory and experiment aspects. Firstly, a new method for calculatingreliability index is derived by determining the normal line of tangent plane at designpoint on the limit state curve. The Hasofer-Lind method with independent randomnormal variables is extended in a generalized stochastic space for arbitrarycorrelative variables. Secondly, a asymptotic approximation formula of structurefailure probability is presented in generalized stochastic space with correlatedrandom variables by the asymptotic method of Laplace integral, by which the failureprobability and risk analysis on the chamfered vertical breakwater have been done.Through the irregular wave experiments in physical model of chamferedvertical breakwaters, ratios of test wave force to calculated wave force by Godaformula are obtained, and the uncertainty coefficient and its statistical parameter ofwave force acting on the chamfered vertical breakwater are presented. Then amodified Goda wave force formula for chamfered breakwater is proposed. The newlimit state functions of chamfered breakwater for anti-sliding and anti-overturningare established, and the reliability index and wave load partial coefficients can beobtained. The proposed values of partial coefficients are given to the current Codefor design of breakwater. Through comparative analyses of reliability of chamferedvertical breakwater with uncertainty coefficients and its different standard deviation,changes of the breakwater reliability and load partial coefficients are studied.