Seismic Assessment of FRP-Retrofitted RC Frames Using Pushover Analysis Considering Strain Softening of Concrete

Seismic actions cause unacceptable levels of damage in existing RC buildings. Existing buildings designed to earlier codes have insufficient lateral resistance, exhibit lower strength and ductility, which induce a global failure mechanism to the structure. Under these circumstances, 'weak-column strong-beam' behaviour dominated the buildings which may lead to the formation of local hinges in the column and so strengthening becomes necessary. In this paper, seismic behaviour of retrofitted RC frames using FRP at joints and steel braces are investigated. For this, moment curvature of the FRP-retrofitted joints are captured by FE analysis considering strain softening of concrete and then pushover analysis for all frames are carried out. Ductility, behaviour factor and performance points of two, four and eight stories frames are then evaluated. The results show that FRP-retrofitting technique can better improve the seismic performance of eight storey frame than steel braces but in low-rise frames, both techniques are beneficial.