Failure analyses of a wind turbine tower under ground motions with different frequency characteristics

Wind turbine tower is a slender high-rise structure with a heavy mass at the tower top. The fundamental period of the structure is generally long; therefore, it may present different failure modes under ground motions with different frequency characteristics. To investigate this issue, a detailed finite element model for a typical wind turbine tower was built in ABAQUS. Based on the response spectrum, two groups of ground motions were selected with two different design characteristic period (0.4 s and 1.1 s). Non-linear time history analyses were performed, and structural failure modes were compared. For 0.4 s cases, since the frequency range for dominant ground motion energy is away from structural fundamental frequency, the tower responses contain more high mode contributions. The initial plastic hinge occurs at the bottom, but full-section plastic hinge and collapse location are at middle-upper part of the tower. For 1.1 s cases, the initial plastic hinge and the collapse section are both located at the tower bottom since structural responses are more affected by the first structural vibration mode. For the same ground motion record, the failure location may vary under different peak ground accelerations.