Stiffness degradation in earthquake damaged and repaired reinforced concrete beams

Abstract

The design of high ductility reinforced concrete (RC) moment frame structures is a well-established practice in regions of high seismicity in New Zealand. Such structures will commonly experience distributed damage and the formation of plastic hinges in the beams of their frames. Understanding the changes in component behaviour can provide context to the post-earthquake performance of ductile RC structures, particularly variations in component stiffness. As part of an experimental investigation on the repair of earthquake damaged RC beams, the degradation in stiffness both prior to and following repair via epoxy injection were assessed. The results suggest that the repair of moderately damaged RC beams via readily available techniques such epoxy mortar and crack injection can have a significant impact on the recovery of stiffness, particularly at smaller levels of deformation, comparable to demands from serviceability level events. The impacts of the epoxy repair were diminished at higher levels of deformation where all specimens under, undamaged, damaged and repaired conditions performed in a similar manner. The results indicate that under moderate levels of damage, where the collapse and life safety performance of a structure can be assessed to no be of concern, simple repair techniques can have an impact at lower levels of shaking, beyond simply cosmetic and durability enhancement.