Reliability Computation Method And Redundancy Optimization Of Port Anchorage Capacity

As one of the vital water function areas,anchorage is widely considered to be a significant part in the development of ports.Therefore,reasonable anchorage capacity planning contributes to better support and guarantee of the port development.Faced with the increasing number of vessel arrivals and the trend of larger-sized ships,anchorage capacity of coastal ports in China,is now suffering growing pressures,which has become an overwhelming constraint on the service level of ports.Hence,it is an urgent need to conduct an accurate assessment of anchorage capacity and optimization of anchorage capacity design in practice.During port planning period,the design anchorage capacity is determined by the demand of ship berthing.However,the actual anchorage capacity is influenced by random factors including vessel arrivals,position of ships in anchorage,ratio of ship types and so forth,which is of considerable uncertainty.Additionally,the design of reasonable anchorage capacity plays an important role in port planning,during which excessive anchorage capacity design will result in enormous waste of resources and inefficient utilization while insufficient anchorage capacity will be a direct threat to port operation and safety.As a consequence,it is necessary to systematically review the random probability characteristic of anchorage capacity and concentrate on the optimization of anchorage capacity planning.This research mainly elaborates a systematic and logical approach of the anchorage capacity reliability compute and the redundancy optimization.Based on a systematic analysis of the uncertain factors of anchorage capacity,the present study adopts Monte Carlo simulation method to establish the probability evaluation model of anchorage capacity,and thus,obtains the probability density curve of the actual capacity of the anchorage under influencing factors such as the vessel size and the number of designed anchoring berths.Following the normal fitting analysis of the probability distributions of anchorage capacity and parameter variations under different design conditions,this study determines to take the number of designed anchoring berths as the main variable and concludes the formula of anchorage capacity probability for “Standard Series” ship model and multiple ship model.Combining this formula with the Queuing Theory Model of probability of vessels in port,this thesis proposed the concept of anchorage capacity reliability together with relevant computing method,followed by the model validation.Considering the system reliability and redundancy optimization theories,as well as the main factors such as objects and limitations in anchorage capacity optimization,the present work sets the number of redundant anchoring berths as the decision variable,aims to achieve both the anchorage capacity reliability maximization and the redundant anchorage area minimization,takes redundancy number limitation,reliability limitation,area limitation and cost limitation as constraints,to achieve the anchorage capacity reliability redundancy optimization model,and brings forward a solution to the model based on the multi-objective genetic algorithm.Finally,this research includes a particular northern port as an example,apply the above computing method and optimization model to explore the relationship between guaranteeing rate and reliability and solve the single anchorage situation,which reveals the trends of redundant number and reliability,and also analyzes the influences of the ship flow density,the number of designed berths and the ratio of ship types on the reliability.Besides,this study tries to achieve the joint optimization of multi-anchorage and get the Pareto Optimal Solution along with the redundancy distribution among all anchorages and the corresponding changes.The result shows that the proposed optimization model can effectively improve the anchorage capacity reliability.Apart from this,the impacts on the reliability vary with the number of designed anchoring berths and the redundancy number.Different combinations of the number of designed anchoring berths,the number of designed berths,the ship flow density and the ratio of ship types influence the redundancy distribution of anchoring berths.The analysis illustrates that more redundant anchoring berths will be allocated to the anchorage which has greater unit redundant area reliability increase.The proposed anchorage capacity reliability computing method and the redundancy optimization model in this thesis provide a solution to the problem caused by the uncertainty of anchorage capacity,and therefore optimize the anchorage capacity.Consequently,the finding of this research is likely to be a theoretical reference for further study in the practical field of port planning.