STRENGTHENING OF COLUMN SPLICES FOR SEISMIC RETROFIT OF NONDUCTILE REINFORCED-CONCRETE FRAMES

Seismic retrofit of existing nonductile reinforced concrete moment-resisting frames incorporates a variety of schemes including adding infill walls, using steel bracing, jacketing frame elements, or a combination of these techniques. One of the ''weak links'' in an existing structure may be the splice tensile strength, which often could limit the benefits of strengthening of other elements in the system. To examine retrofitted-splice behavior, several different strengthening approaches were considered Twelve two-thirds scale specimens with column splice details typical of ordinary moment-resisting frames were strengthened using different techniques. The procedures used included welding spliced bars, confining the splice region with steel elements such as angles and straps, and providing steel reinforcing bar ties externally or internally in the splice region. They were intended to provide continuity or to confine the bars to prevent splitting of cover in the splice region.