Reliability Analysis Of Vertical Breakwaters

Breakwaters are important components of port projects. They take large proportions in port projects total investments. It is disastrous if the breakwater is broken down. Vertical breakwater widely used is port projects is an important type of breakwaters. It has both high theoretical meaning and high engineering value to research the reliability of the vertical breakwaters.The Full Probability Method(Level III Method) is adopted to calculate the reliability of structures initially. The Full Probability Method develops slowly because of the restrictions of the calculation level and mathematics methods. On the contrary, Approximate Probability Method (Level II Method) develops rapidly because of its simple calculation and accuracy to meet most of the projects, in which First Order Second Moment Method is most widely used. The Full Probability Method is used more widely with the development of computing technology.The committed steps of the Full Probability Method are choosing the joint density function and calculating the integration on the failure domain. In this article, the commonly used two-dimensional joint density functions are summarized. The numerical integration method is used to calculate failure probability directly if the joint density function of the variables is known. In case of the joint density function unknown, the joint density function is constructed by NATAF transformation. Then the numerical integration method is used to calculate failure probability.The main loads are the wave pressure and the uplifting pressure when calculating the reliability of a breakwater. The variable-incorrelate JC method's calculation accuracy is not high because it doesn't consider the correlation of the wave pressure and the uplifting pressure. In 1992, based on the analysis of the domestic wave frequency, Xie Shileng and Liu Ying proposed that Log-normal distribution or Gumbel distribution can be used to describe the long term distribution of the wave load. In this article, the wave pressure and the uplifting pressure both use Gumbel distribution as their long term distribution. There are Poisson Mixed Gumbel Distribution and Poisson Logic Gumbel Distribution in two-dimensional joint Gumbel distribution. One essential condition to use Poisson Mixed Gumbel Distribution is the correlation coefficient of the variables must in . Most of the correlation coefficient of wave pressure and uplifting pressure is greater than . Thus, Poisson Logic Gumbel Distribution is used as the joint density function of wave pressure and uplifting pressure.The breakwater in Qinhuangdao is taken as an example to inspect and verify the direct integration method. It can be concluded that the direct integration method and the variable-correlated JC method have similar results and the variable-incorrelate JC method's calculation results are obviously lower.