FINITE ELEMENT ANALYSIS OF SEISMIC BEHAVIOR OF RC FRAME JOINTS INDIRECTLY STRENGTHENED WITH TIED AND LOCK-ANCHORED CFRP SHEETS

The method of indirectly strengthening RC frame joints with tied and lock-anchored carbon fiber reinforced polymer ( CFRP) sheets can effectively avoid debonding of CFRP and infeasibility in practice which exist in strengthening directly． Based on the numerical simulation comparative analysis of the five strengthened joints' hysteresis curves， bearing capacity and ductility coefficient， the influence of the parameters on the seismic performance of the joints strengthened with tied and lock-anchored CFRP sheets was discussed． The influencing parameters included the ratio of stirrup ，longitudinal CFRP sheets at the beam end and the amount of lateral shear CFRP at the beam and column end． The results showed that the tied and lock-anchored CFRP sheets could significantly improve the seismic performance of the joints． The maximum increase in ultimate bearing capacity and ductility coefficient of beam end was up to19. 8% and 55. 5% respectively． When others remained invariable， increasing the ratio of longitudinal CFRP sheets at the beam end could simultaneously improve ductility and bearing capacity of strengthened joints，but the ratio of stirrup at the beam end could only improve the ductility significantly． Increasing the amount of lateral shear CFRP had little effect on the ductility and bearing capacity of strengthened joints，but it could effectively delay the yield and bonding-slip of the longitudinal bars．