Seismic Performance of Repaired Lightly Reinforced Concrete Walls

Presented by Christopher Motter, Washington State University

As a result of the 2010-2011 Canterbury earthquakes, over 60% of the concrete buildings in the Christchurch Central Business District have been demolished. This experience has highlighted the need to provide guidance on the residual capacity and repairability of earthquake-damaged concrete buildings. As limited testing has been performed on repaired components, this study focuses on the performance of severely-damaged lightly-reinforced concrete walls repaired through replacement of reinforcement and concrete in the damaged region. The damage prior to repair included buckling and fracture of longitudinal reinforcement, crushing and spalling of concrete, and, for one of the two walls, out-of-plane instability of the gross section. Prior to repairing the walls, tensile testing of reinforcement with welded connections was conducted to verify acceptable performance of welds suitable for reinstating the damaged reinforcement. Repairs to the walls consisted of removal of damaged concrete through either hydro-demolition or jack hammering, followed by cutting and removal of damaged reinforcement and reinstatement of new reinforcement and repair mortar. The two repaired walls were tested using a standard reversed-cyclic loading protocol that was identical to that used for one of the two original walls. Aside from a difference in the elastic stiffness, the load-deformation responses of the repaired walls were similar to that of the originally-tested wall through to the first loading cycle at 2.0% drift, beyond which strength degradation was more pronounced for the repaired walls. The overall performance of the repaired walls relative to the original wall indicates that it is feasible to achieve acceptable performance of severely-damaged concrete walls repaired through replacement of reinforcement and concrete in the damaged region.