Study On Seismic Fragility Of Reinforced Concrete Tower Based On Cloud Method

With the rapid development of new energy,the wind power industry has ushered in new opportunities,and the steel-hybrid combination tower technology of wind turbines has broad application prospects in the development of wind power energy in China due to its advantages of large rigidity and good fatigue resistance.Steel-hybrid composite tower is composed of reinforced concrete tower and steel tower,its structure is similar to the gradually narrowing cantilever beam,the failure of any section has a fatal impact on the overall structural safety,the disaster sensitivity is higher,and compared with the upper steel tower,the lower reinforced concrete tower as the main structure is more likely to be damaged under the action of earthquake.In this paper,combined with the seismic damage characteristics of wind turbine structures,the damage law and seismic vulnerability of reinforced concrete towers are studied through evaluation methods and calculation analysis.The main research contents and conclusions of this paper are as follows:(1)The blade-tower-base-foundation coupling system model is established,and the structural self-vibration characteristics are analyzed based on the structural dynamics theory,which verifies the correctness of the model.The effect of infinite domain foundation is simulated by infinite element boundary and viscous-spring boundary,and the concrete plastic damage constitutive is introduced,the seismic response law of wind turbine under boundary effect is compared,and the weak part and damage development law of reinforced concrete tower are explored.The results show that the acceleration time history and displacement time history response laws of each feature point under the two boundary conditions are basically the same,and the response value is increasing with the increase of height,and the damage law of the tower under the boundary effect is basically the same,first the damage is generated at the door opening,and then it spreads to both sides of the door hole and the upper side area,and then the damage occurs in the middle and upper gradient section of the tower,the above areas are all seismic weak parts,and it is necessary to strengthen the reinforcement design or section optimization,and finally improve the seismic performance.(2)Based on the seismic intensity evaluation system,the validity,adequacy,correlation,practicality and beneficiality of five basic amplitude ground motion strength parameters were evaluated by selecting a total of 100 ground motion records in the near and far fields.After comprehensive analysis,it is found that compared with the more common PGA and other less commonly used seismic intensity parameters,PGV is more suitable as a strength index for evaluating reinforced concrete tower structures.(3)The probabilistic seismic demand model of reinforced concrete tower barrel was established by selecting PGV and horizontal displacement Angle,and the vulnerability curve of tower structure under near and far field earthquakes was constructed based on the cloud method.The analysis shows that there is a tendency in both to develop the structure of the tower from basically intact,slightly damaged to moderate damage to severe damage and finally even collapse,the vulnerability curve of the structure gradually becomes smooth,and will no longer be as steep as the first performance level state.This shows that as the damage state becomes more serious,the probability of overtaking the limit state is decreasing,and the damage effect is far less obvious than at the beginning when the seismic intensity value increment is the same,and the overtake probability of near-field ground motion in the same limit state is generally significantly higher than that of far-field ground motion.