Prediction of seismic bearing capacity of unbonded post-tensioned precast concrete frame joints

In order to study the seismic bearing capacity of unbonded post-tensioned precast concrete frame beam-to-column joints, a calculation method for the skeleton curve of joints is proposed. First, based on the elastic beam deflection and rigid body rotation theory, the composition of displacement of the unbonded post-tensioned joints is analyzed and the common formulas are given. Then, according to the loading features of the section at the beam end at different critical points (crack points, linear critical points, crush points of the core concrete), the corresponding loads are calculated. Finally, according to the rotation features and the hysteretic model of the angle of the unbonded post-tensioned steel angle joints, the simplified formulas for the characteristic points of the skeleton curve are deduced. The calculation results agree well with the experimental results under reversed cyclic loading, proving the rationality and correctness of the calculations. The results show that based on reasonable rational mechanics, this calculation method, which is simple and widely used, can predict the skeleton curve of joints accurately.