The Axial Bearing Capacity Of Large-diameter Grouted Connections For Offshore Wind Turbines

Pile foundation is popular in the offshore wind power engineering,and the grouted connection is used to connect the pile foundation and transition piece.Large-diameter grouted connection is the key component of the support structure of offshore wind turbine,and its bearing capacity and allowable deformation are strict.So it is very necessary to carry out the research on the bearing capacity of large-diameter grouted connection.The research contents and results are as follows:(1)Research on constitutive model for high strength grout.Uniaxial compression tests and low cyclic compression tests of high strength grout are carried out,and the ultimate compressive strength,stress-strain curve in cyclic loading and cyclic residual deformation of high strength grout are measured.The damage characteristics of high strength grout under cyclic compression are obtained.The above work provides the parameters for determining the brittle cracking constitutive model and damage plastic constitutive model.(2)Study on shear capacity of steel plate-grout with shear keys.Shear tests with different initial normal stress and different shear key height-to-distance ratios are carried out to explore the influence of initial normal stress and shear key parameters on shear strength,and to analyze the crack growth process of grout.The shear failure process of steel plate-grout with shear keys is numerically simulated by the brittle cracking constitutive model,and the shear-slip curves and the crack development of the grout are consistent with the experimental results.(3)Study on bearing capacity of grouted connection under axial load.Axial compression tests of grouted connection with different diameters and different shear key height-to-distance ratios are carried out to research the influence of the design parameters on the axial bearing capacity of grouted connections,and to analyze the bearing mechanism and the failure mode of the grout.The axisymmetric finite element(FE)model of grouted connections is established by using brittle cracking constitutive model,and the shear force-displacement curves,the fracture and failure modes of the grout are in agreement with the experiments.Based on the equal principle of radial stiffness,the shear stress of large-diameter grouted connection is predicted by using the double shear test with shear keys,and the regression equation between the shear stress and the radial stiffness of grouted connection is proposed.(4)Study on bearing capacity of conical grouted connection under axial load.Through the axial compression tests of the conical grouted connection,the characteristics of load-displacement curves are studied.Three dimensional FE model of conical grouted connection is established by using the elastic plastic constitutive model for steel tube and the brittle cracking constitutive model for grout.The bearing behavior of conical grouted connections and the cracking process of the grout are simulated by this FE model.According to the tests and FE results of conical grouted connections,the bearing mechanism of conical grouted connections and the crack growth pattern of the grout are obtained,and a new method for calculating the bearing capacity of conical grouted connection is also presented.