A CALCULATION MODEL FOR THE SLIP MOMENT-ROTATION OF REINFORCEMENT BOND

The longitudinal reinforcement slip at the beam-column or footing-column interface significantly increases the lateral deformation. The envelope curve of the moment-rotation model caused by this slip is usually idealized as a bilinear curve. This study modified the bilinear curve and proposed the calculation model for slip rotation of yielding and failure points. Compared with the experimental results of 24 circular columns in five independent batches, the accuracy of the model was verified. This bond slip moment-rotation model was simulated in software OpenSees, and the force-based element was selected to model columns. The numerical simulation of cyclic tests of circular columns showed that the calculated results were in good agreement with the test results. Furthermore, time history analysis was conducted to simulate shake table test, and the results demonstrated that both top displacement and bottom slip rotation were well predicted. The results of parameter analysis showed that the ratio of slip deformation to total lateral deformation at the failure point was about 30%-40%, and both the increase in the column axial compression ratio and the decrease in the volume ratio of stirrups would reduce this ratio.