EXPERIMENTAL STUDY ON SHEAR MECHANISM OF PERFOBOND CONNECTORS IN WIND TURBINES FOUNDATION

Because fatigue fracture of steel bars had occurred in perfobond connectors of wind turbines foundation, 4 different groups, totally 12 push-out tests were carried out to provide evidence for the design of wind turbines foundation under extreme and running condition. Test specimens were designed to have many perfobond connectors along the direction of shear load considering the structure of wind turbines foundation and pre-existing push-out test of PBL shear connector. Test results show that the failure process of push-out test includes three stages, the interface friction between concrete and steel plate, the concrete tenon holes of perfobond connector resisting shear load, and the steel bar of perfobond connector yielding and its upper concrete crushing. Compared with the case of no steel bar perfobond connector, the strain results of steel bar and plate show that the bending stress on bottom steel bar is more obviously because of the shear stress on upper steel bar, and the shear capacity of specimen is significantly improved. During the failure stage, the stress state of steel bar changes from bending to shear, and the steel bar yields with the crush of its upper concrete. Because 3 steel bars all yields gradually with the growing of vertical cracks, the strength and plasticity of specimen is fully developed. 3 steel bars or 2 steel bars locating at the second and third perfobond connector is suggested in the design of wind turbines foundation. Based on this test results, the shear strength formula of perfobond connector in wind turbines foundation was put forward. Compared with tests results, the calculated value tends to be a little conservative, and can be used for the design of wind turbines foundation.