Damage and Seismic Performance Assessment of FRP-Retrofitted Multi-Storey RC Buildings

Abstract

Structures should be designed for a long in-service life at the lowest cost. Performance based design (PBD) can be used for damage and performance assessment of older FRP-retrofitted multi-storey RC moment resisting frames (MRFs). PBD can be performed using nonlinear pushover analysis according to current codes. In this paper, performance of an existing/older RC frame that has been retrofitted with steel-braced by other researchers is assessed in order to evaluate the ability of the FRP-web bonded system to upgrade the performance level and ductility of RC MRFs. Initially, the flexural stiffness of FRP-retrofitted exterior and interior joints of each level of an existing RC ordinary moment resisting frame (OMRF) is determined using nonlinear finite element (FE) analysis. The stiffness obtained is then used in a mathematical model for pushover analysis of the FRP-retrofitted frame. The plain and the retrofitted frames (both steel-braced and FRP-retrofitted) are analysed using a nonlinear pushover analysis method. The seismic performances of the retrofitted frames are then compared with the plain frame. Finally, the global damage index of the frames at the performance point (and at the life safety (LS)) are determined from the capacity curves and discussed. This evaluation demonstrates that the damage degree of the frame is reduced after retrofitting particularly by FRP. In addition, the FRP-retrofitted frame has a lower damage index at the LS level.