Development Of A Strain Health Monitoring System For Jacket Platforms And Prediction Of Fatigue Life

Jacket platforms have been exposed to various environmental loads in harsh marine environments for a long time,resulting in frequent accidents due to fatigue damage.Due to the complexity of the structure composition and working environment of the jacket,factors such as sea wind,waves,and currents have caused endless fatigue failures of key weak parts of the jacket platform during operation,seriously threatening the safe operation of the jacket platform and the safety of staff.In order to prevent large-scale safety accidents from occurring due to the fatigue aging conditions of active jacket platforms during service,the strain health monitoring and early warning of active jacket platforms needs to be addressed.However,relatively complete structural health monitoring technology involves interdisciplinary fields,and there are problems such as difficult monitoring of load signals,difficult processing of online data,and difficult assessment of damage status.Therefore,in order to ensure the safety and reliability of jacket platforms during service,strain health monitoring and fatigue life prediction for jacket platforms are crucial.The main work of this paper is as follows:Carry out the overall scheme and hardware equipment design of the jacket platform strain health monitoring system.Firstly,the composition and functions of the strain health monitoring system are analyzed to determine the composition and functions of the hardware and software of the strain health monitoring system.Secondly,the overall plan of the emergency health monitoring system is formulated,including the design of hardware equipment and software development.Finally,according to the design requirements of the overall plan of the strain health monitoring system,the hardware equipment used in the strain health monitoring system is designed,including the design of sensors,acquisition instruments,industrial control computers,and power supply devices.Develop software for a jacket platform strain health monitoring system.The software development includes two modules: strain data acquisition and fatigue life prediction for jacket platforms.The strain data acquisition module is composed of sub modules such as a user login module,a collection and display module,a storage and playback module,and a key parameter setting and status display module.Its main functions are to manage users,collect and display measured strain data,store and playback,and set various sampling parameters as needed.The fatigue life module is composed of sub modules such as the platform basic parameter module,strain data processing module,fatigue life evaluation module,and monitoring and early warning module.It realizes the functions of displaying the platform basic parameters,processing measured strain data,extracting cyclic stress spectra,calculating fatigue damage and life,and real-time early warning.Carry out feasibility experimental research on the strain health monitoring system for jacket platforms.Firstly,the static analysis of the finite element model of the jacket platform was conducted to determine the location of dangerous nodes on the jacket platform.The actual installation location of the strain sensor was determined based on the specific conditions of the laboratory platform structure.Secondly,the feasibility of the developed strain health monitoring system for jacket platforms is verified through sensor calibration experiments and joint debugging experiments of the strain health monitoring system.Finally,the laboratory jacket platform is loaded by simulating the wave loads on the offshore jacket platform during different periods of time,and the measured strain data under different loads are obtained,providing the measured strain data for the subsequent fatigue life prediction.Carry out research on fatigue life prediction of dangerous nodes based on measured strain data.Firstly,the stress concentration coefficient of tubular joints is calculated using the finite element method.Then,based on the measured strain data,the cyclic stress spectrum of hot spots is obtained using the hot spot stress method and the rain flow counting method.Finally,the fatigue life of dangerous joints is predicted based on the selected S-N curve of tubular joints and the linear cumulative damage theory,and the fatigue damage and life of A1 and A4 tubular joints under different loads are obtained.