Research On Calculation Of Hull Structural Reliability Based On Monitoring Information

Mostly,the destruction of hull structure is not a occurrence of sudden.In general,the extent of the damage is accumulated during its service voyage,resulting in the damage of structure failure.Hull structural health monitoring system can monitor the real-time structural response under the external loads.Using these data can always predict the extent of "hull structure health degree".Apparently,the value of reliability can be used to characterize the "healthy degree" of the hull structure.This dissertation provides a real-time reliability calculation method based on the information collected by the hull structural health monitoring system which is installed on an in-service ship.The real-time sample information can be collected by hull structural health monitoring system to reflect the current stress levels of the hull structure.In this dissertation,Bayesian method is used to achieve a self-updating program of monitoring information.The so-called self-updating means that the monitoring system can sum up each time stress information which involves history statistics and present samples to achieve new scientific statistics values.These statistics values are applied to the next reliability calculation step by the way of probabilistic model.When the present probabilistic model is updated,the present structure reliability can be calculated by using statistics characteristic values which can be got from the updated probabilistic model.Finally,the functionality what can forecast present "hull structure health degree" can be achieved.In order to achieve this functionality,this dissertation provides the following methods:(1)The method of how to deal with monitoring information data is provided.This method is used to transform monitoring information data to available statistics probabilistic model,which involves sample generation,statistical calculation and fitting the sample data;(2)The method of updating information data based on Bayesian theory is provided.Firstly,this dissertation derives formulae which are used to update the probabilistic model that the data samples may obey based on Bayesian theory,and then used these formulae to design self-updating program;(3)The method of hull structure real-time reliability calculation is provided.After receiving the updated probabilistic model,this dissertation gives different reliability calculation methods for different kinds of probabilistic model.To sum up,the reliability calculation methods which are provided herein are based on FOSM method and Monte Carlo method.Above all,a calculation method of in-service ship hull structural real-time reliability based on monitoring information is given in this dissertation.Simultaneously,this dissertation gives the relevant calculation examples according to the actual information of a ship sailing in a certain area,and then the calculation results and briefly relevant analysis are provided as well.