Fatigue Life Research Of Storage Tanks In-service Based On Foundation Settlement Prediction

Due to the industrial development and national strategy,most of our national petroleum reserve bases are located on the soft soil area along the coast.The soil property is complex and the storage tank foundation is prone to uneven settlement.That will lead to greater peak stresses on the storage tanks and may result in fatigue failure of the tank during turnover.In this thesis,the change of foundation settlement value with time and the contact relationship between tank bottom and foundation are considered,which help to establish the fatigue life analysis method of storage tanks in-service based on foundation settlement prediction.This method is used to predict the fatigue life of storage tanks in engineering.Finally,the influence of different factors on fatigue life of storage tanks in service is discussed.The main research works of the thesis include:(1)The foundation settlement charaters of storage tanks in-service is studied.Based on the settlement data of tanks in-service,Exponential curve method,Poisson curve method and Grey theory method are used to predict the settlement of the tank.The predition methods are programming in MATLAB for computing automation.The accuracy of the prediction results is compared which shows that the Exponential curve method is the best of the three.Therefore,Exponential curve method is chosen to predict the foundation settlement of storage tanks in engineering.(2)A new elastic ring foundation-tank contact model is introduced based on the situation of foundation uneven settlement of storage tanks in-service.This model is applied to the finite element simulation.A fatigue life prediction method of storage tanks in-service is submitted based on the model which is applied to engineering to analyze the fatigue safety of storage tank in-service due to uneven circumferential settlement.The results show that this method can predict the structural fatigue life of storage tank under uneven settlement,which would provide guidance for the safe use of the tank.(3)The finite element method is used to calculate and analyze the influence of the value of uneven circumferential settlement and local uneven settlement on the fatigue life of the tank under uneven foundation settlement.The results show that the influence of these factors on the peak stresses of the tank is significant.