Study On Fatigue Bearing Capacity Of The Grouted Connection Of Offshore Wind Turbine

As a clean and stable renewable energy source,offshore wind energy is a strategic choice to alleviate current energy shortages and solve environmental troubles.The design of offshore wind turbine infrastructure is the focus of offshore wind farm construction,and the safety and reliability of grouting connections in the infrastructure is the key to ensuring the normal operation of offshore wind turbines.Grouting connection has become one of the main connection forms of offshore wind turbines due to its advantages of convenient underwater construction,high anti-overturning bearing capacity and large geometric redundancy.The bearing capacity of grouted connection of offshore wind turbine structure under complicated loads needs to be studied under current circumstances of rapid development of offshore wind energy.Focusing on the grouted connection,the research of this thesis includes following contents and conclusions:1.In this paper,a series of high-strength grouting material test block static loading and fatigue loading tests are carried out.We studied the mechanical properties of the test block.The failure mode,compressive strength,load-displacement relationship and stiffness degradation characteristics of high-strength grouting materials are mastered.The damage plasticity model parameters of high-strength grouting materials are obtained,and the calculation accuracy of the constitutive model parameters is verified by comparing the cyclic pressure test results of different load levels.The damage evolution law of the test block under static loading and the non-fatigue loading test block are obtained.The fatigue damage calculation method of high-strength grouting material is proposed.2.According to the axial bearing capacity of grouting connection,the influence of radial restraint on bearing capacity is discussed.Through the test combined with numerical simulation method,the failure mode,stress-strain relationship and load-displacement relationship of grouting joint under axial force are systematically analyzed.The damage area of grouting body and the law of damage evolution are mastered,and the calculation method of damage variable under axial load is proposed.Based on the numerical simulation of the grouting connection design parameters in the actual project,the relevant suggestions for the design optimization of the fan grouting connection section in the actual project are given.3.Aiming at the axial fatigue bearing capacity of grouting joints,a series of axial compression fatigue tests of grouting joint scale model specimens were carried out,and the load size,cycle number,circulation sequence and sudden load were analyzed systematically.According to the influence of fatigue bearing capacity,the failure mode of the grouting connection under the action of fatigue load,the relationship between the displacement-loading times and the nonlinear damage accumulation mechanism of the grouting body and its development law are established.The damage of the grouting body and the residual axial bearing capacity are established.The relationship between the residual bearing capacity of grouting connection based on damage is proposed,and its application in practical engineering is given.4.For the bending bearing capacity of the grouting joint,the static bending test and the low cycle bending test of the scale model are carried out.Based on the experimental results,the bending behavior,failure mode and displacement-moment relationship of grouting joints are analyzed and discussed.The damage area and damage evolution law of grouting body under bending moment load are mastered.The damage variable calculation method is proposed,combined with numerical simulation.The method is to establish a numerical model for the connection of large-diameter single-pile foundation grouting,analyze and discuss various design parameters,and propose design suggestions for practical engineering applications.In this paper,the bearing capacity of grouting connection is systematically studied and analyzed from theoretical analysis,numerical simulation and model test.The method system of grouting connection structure design is formed,which provides a research basis for the application of grouting connection technology.