| Abstrakt: |
Under disastrous earthquake conditions, the bolted spherical joints in spatial steel grid structures are prone to bending, breaking, and other failure modes, and their failure has obvious ultralow cycle fatigue failure characteristics. In this paper, quasistatic tests were carried out on three groups (nine specimens in total) of bolted spherical joints with joints at both ends under uniaxial cyclic loading. The failure characteristics, hysteretic behaviour, bearing capacity degradation, stiffness degradation, and energy compression capacity of bolted spherical joints under three loading schemes were studied. At the same time, the change rule of the rotation angle with the number of cycles was obtained. The experimental study shows that each member experiences characteristic moments of high-strength bolt bending, cracking, crack propagation, and a loud crack and that bolt failure occurs at the middle bolt ball connection. The ultimate ultralow cycle fatigue failure of the specimen occurs after more than 10 cycles, and the energy compression capacity is poor due to the small volume of high-strength bolts and sleeves. The "pinching phenomenon" of the hysteresis curve of the bolted spherical joint is serious. The tension area of the hysteresis curve increases, and the fullness of the compression area decreases, with increasing tensile amplitude. Based on the cumulative energy compression, a damage model suitable for bolted spherical joints under cyclic loading is proposed. From the experimental data, a correlation formula between the angle change rate and the damage model was established when the middle bolt ball of the connection specimen experienced a tension–compression cyclic load. This formula provides a reference for the evaluation of bolted spherical joints of bolt ball grid structures after an earthquake. [ABSTRACT FROM AUTHOR] |
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